555 Timer To Control Motors

Did you place the motors in the circuit in the location labelled device in the schematic?

Yes, the positive is connected there and negative onto the battery. I also used stripboard like in the diagram.

The 555 timer chip is a rectangle with a indented o on the top, i assumed this was equivalent to the cutout semi circle (please tell me i don't have the chip the wrong way around).

With the chip package in the orientation you describe, pin 1 is at the upper left, pin 2, 3, and 4 are below it, in order, on the left side. Proceeding around the package in an anticlockwise direction, pin 5 is at the lower right, then 6, 7, and 8. Pin 8 is opposite pin 1, at the upper right corner of the package.

Besides bipolar transistors like the '3055, you might also consider using a power MOSFET to drive your motor.

-e

I have just had a look at the circuit and to run a motor you need a transistor to handle the current, it is most likely you have burned out the internal device. It can only handle 100ma or so. You need a power device and it should have the base connected to pin 3 then the collector to +V and emitter to the motor put a diode across the the motor terminals cathode to +V terminal with a 0.1uF cap ceramic 32v for up to 12V supply. Use an NPN Tr. BFY50 or 2N3055 TIP3055 with a heat sink. You may need to use a Darlington configuration if the current is above 1.5 amp for the motors, remember the starting current for a small DC motor can be 10 to 20 times is running current, and any load will demand a proportion more than no load. It depends on the torque required. I hope this helps you out some.

Thankyou, I will do my shopping needed to get the parts on monday and see how i go from there.

Thanks again.

Above instruction is perfect.

Let me add the information that chip 555 is just a "timer" that required an additional power amplifier to deliver adequate power to a motor.

Here it is suggested a NPN power transistor. Be sure the output from 555 has also reverse diode protection as output from power transistor (another diode reverse polarity connected in parallel to motor windings (In to motors). Electronic / semiconductor devices are easily damaged by voltage spikes produced in inductive (motor windings) load switching circuits.

Proper student's project should have at least two stages: the circuit assembled on breadboard and second (final after successful tests) soldered on PC board.

Good luck!

BrainWave,

Tell me more about this so calls 555 or 556 timer. I have a small dc12volts circuite board operating with Aromat time unit (Cn-C Time Unit # CNC-JP-DC12V). I would like to know if I can replace it with 555 timer? This board is part of the Main board to operate my old printing machine. Please give me your input.

Thanks,

Thada

The 555 timer was introducted by Signetics in the 1970s and is nearly ubiquitous in its application where simple timing circuits, oscillators, pulse-width modulators, and so forth are required. It is very inexpensive and is still hugely popular with electronics enthusiasts. Here are a few links to web pages dedicated to this chip. Be sure to copy and paste the entire address into your brower's address bar (my apologies for not making these hot links, but I'm using MacIntosh Safari which cripples CR4's message editor (no italics, bold and underline, spell-checker, links, pics, etc., and it eats whitespace so that paragraphs, bulleted lists, etc., are rammed together into one piece of monolithic text). http://www.uoguelph.ca/~antoon/gadgets/555/555.html AND http://cr4.globalspec.com/edit/newcomment?objectid=6375&objecttype=THREAD&c=47647 AND http://home.cogeco.ca/~rpaisley4/LM555.html AND http://www.kpsec.freeuk.com/555timer.htm . This should get you started. -e

Use a power transistor 2N3055 to drive the motor. Use H-bridge if you wish to change the direction also.

use japanese capacitors and water cooling around H bridge.

-a firend.

That is the safe Half bridge that can drive from TTL source. Other side of motor is connected to either GND or Power source. This will work in both conditions as it has source and sink. It is also possible to use voltages up to 24V. I have more safer circuits also now.

Guest wisely posts: "use japanese capacitors and water cooling around H bridge." ----- Yes, especially if you're driving 4000 HP three-phase synchronous DC motors. If water cooling proves ineffective, you can always immerse the bridge in beer. I recommend a hearty guiness with a twist of lime. :-)

I just had a look at the circuit diagram for the 555 timer chip and the output is current limited so you should not have burnt the chip out by trying to drive the motor directly. I agree with the other, except the water cooling part, that the only solution is to add a transistor that is capable of driving the motor.

Dear Mark

You are right. Adding transistors helps. Here are two designs of half and full H-bridge which I designed for students.

its my first time here..this is interesting..i m only a pilot and i dont have much knowedge in electronics is just a Hobby..but my strenger designed circuits are alwys to sutisfy my needs..

like ..i like that curcuit of Mr. Ghuru. using 2N3055..there fore forced to register just now, (however i m off topic a bit) i got a circuit that have a solenoid to alter flux of a permanent magnet in a soft iron core material with squre wave +/- altenating 1 Amp, current.. so to have a variable frequency range from 40Hz to 100hz i decided to use 555 and followed by dual 4027 flip flop of which (j,k,Clock) joined together so i decided one output of flip flop to a H brigde and other output to a second input of H brigde...to have a altenating current so i want to asking if ths H-bridge my torelate those frequeny ...i hope it may work and any delay to leg out my expected result...

i was smulating it on yenka software but fail to get a good higher current H bride enough to drive this device...

i will appreciate you input...thanks in advnce to all

G'day gals, guys & gurus,

This is slightly off topic but since were talking about control circuits and using 555 timers I thought you may be interested in my latest project.

It's a model of the Starship Enterprise NCC-1701A from the movie and to make it more interesting I decided to add lights and the ones like the anti-collision strobes, navigation lights, warp drive etcetera need to flash and at first glance a 555 timer would be the way to go.

However, that would involve having fixed patterns of flashes that once wired in could not be altered so I decided to finally bite the bullet and figure out how to use microcontrollers.

Some time back I purchased a PICkit2 from Microelectronics that comes with a small prototyping board. 16F690 microcontroller and USB programmer that can be used to download and program the microcontrollers.

It took a couple of weeks (closer to a couple of months) to get up to speed and find the software that works best for me, but in the end I will most likely never use anything more than a microcontroller in any of my electronic designs. Basing your electronic designs around microcontrollers rather than discrete components may sound like overkill but the added flexibility, simplicity, cost, ease of use etcetera makes the use of microcontrollers by far the best solution for the average hobbyist electronic guru regardless of what you are trying to do. It also means that you can change the way your electronic device works by reprogramming the microcontroller thus making it virtually idiot proof.

So what do you need to know about microcontrollers?

Not that much really. Once you get your head around what they are capable of (which is pretty much anything you could imagine) it's a pretty simple step to design a circuit and program the microcontroller to do what you want. Here are some links to the items you will need to get going.

• Microcontroller: First off you need to find a microcontroller that will do what you want. For med this is the PIC16F690 which has up to 18 programmable IO ports. If you buy them in bulk like I do (batches of 20) then they are actually cheaper than a standard 555 timer chip and a couple of million times more useful.
• Programming Unit: Next up you will need to invest in a programming unit. This is basically an interface that goes between your computer and the microcontroller that enables you to download the program you have written onto the microcontroller. You can build one of these yourself, usually utilizing a microcontroller, but I would recommend using a ready made one. In my case that's the PICkit2 from Microchip (see image below) that can be purchased from Microchip for US$49.⁹⁹.
• 
• Compiler: Microcontrollers need to be programmed utilizing what is referred to as machine code. Basically this is a series of instructions that the processing core of the microcontroller executes. Now you can write programs directly in machine code, but I would not recommend going down this path unless you have previous experience in writing machine code. Instead you can use a compiler that can take complex instructions that then translates them and generate the machine code that the microcontroller can understand and run. Like the programming unit there are a myriad of compilers available, some for free others need to be purchased. In my case I went for the freeware Great Cow Graphical BASIC which is a flow chart orientated compiler based on Great Cow Basic. Basically it allows you to design your program by utilizing flow charting symbols under windows, then when you are happy with the program it translates it into Great Cow BASIC instructions that are then compiled into the machine code your microcontroller understands. It's then a simple matter of loading the machine code onto your microcontroller utilizing the programming unit discussed earlier.

That's about it. Yes it sounds like a lot but in reality a week or so of your time will get you to the stage where you will wonder how you did thing before microcontrollers. It's really that simple and if like me you have a myriad of applications, once you have perfected you circuit design you can use it when and wherever you like just by writing a new program for the microcontroller.

If you really get into utilizing microcontrollers and that's not difficult, then you may wish to design and build your own boards from scratch. For this I recommend the following:

• TinyCAD: This is a nice little program that you use to design your circuit. It takes a while to become expedient with it but it's well worth the trouble and will generate what's called the NET List which is ultimately used to design the printed circuit board layout.
• FreePCB: Like the title suggest this is free. Basically this takes the NET List generated by TinyCAD and combines it with component footprints to generate a view of the physical printed circuit board layout. You then utilize the various tool that the package contains to move the components about and design the track layouts of your printed circuit boards. Unfortunately FreePCB is still a work in progress and it not capable of generating the final printout that is used to generate the transparencies used to create the PCB. However, there are several ways to get around this problem so if you do decide to use it to design your PCB then drop me a line and I will explain how to get around it.

Well, that's about it. I really do recommend taking the time to learn how to use microcontrollers and design the circuits to go with them. They really are very simple to use and I can guarantee that you will wonder how you ever built anything electronic before.

Happy microcontroller designing,

masu

Could you sell your work?

Or just freely spread the diagram?
Nice to see you after 3 years!

G'day gals, guys & gurus,

• Could you sell your work? Or just freely spread the diagram?

I'm currently working on a range of circuits that consist of:

• Master Control Board: This is a PIC16F690 board that has 14 inputs/outputs that can be used to switch loads of up to 100 mA per output. The remaining four IO ports on the 16F690 are connected via a bus interface switch to a programming bus that connects an technically unlimited number of control boards that can then be programmed by connecting the PICkit2 to the bus. The individual board is then selected by placing a magnet near the board which operates an on board reed switch that in turn connects the microcontroller to the programming bus and places it in program mode.
• Secondary Output Board: This is just a simple TIP32 based board that takes one output from a master control board and allow you to drive up to 40 outputs with a total current drain of 3.0 A
• Interface Board: This is just a simple board that distributes the power and programming bus to the various boards imbedded within whatever it is you are controlling. It's only intended to keep things tidy and suppress my need for things to be neat and ordered so it's not absolutely necessary. I may also add a power supply circuit to this board so you can power the system from a wall wart type power pack.

They are still at the prototype stage and it will take a couple of months before they are finished and I have all the bugs ironed out.

Anyway, when I'm happy and sure the things work I will make the circuits, layouts and artwork available to for free provided they are for personal use and not sold to third parties or mass produced.

Regards, masu

It will be really SOMETHING!

If you have a Teacher Soul - write down steps from designing to tests / starting.

An author of an Electronic Systems' Book shall buy your idea!

G'day gals, guys & gurus,

I have been somewhat lax of late but I will be documenting both the electronics and construction of the Starship Enterprise model on my "masu on" CR-4 blog under the Mozzie section. Originally this was intended to cover the construction of a flying model of the deHavilland DH‑98 Mozzie from WW‑II but that project is on hold for technical reasons so I have expanded it to cover all my modelling projects.

Regards, masu

Dear Masu,

It is not so good to put a lot of power in signals on the Microcontroller board as you never know how many signals one will ever need and which type of signal sense and control one will end up. It is good to pass power ground and both sense and control TTL level to the interface boards and then do the signal conditioning at that end as it is required.

One small transistor could drive high power relays that can switch SPDT or DPDT mains power using 12V 100mA through a transistor like 2N2222 or 2N3904 or BC548 etc.

Some people preferred ULN2003 type driver IC with 500mA maximum drive power and higher voltage switching transistor output and also with diode protection. I think, this option was good, but I still prefer discrete transistors.

For sense signals I am often using signal to frequency converters and using uC power to count these pulses to digitize the signal. This is usually a good way rather than using an ADC. For real industrial applications, ADC to be preferred. I am using 16-bit ADCs right now for industrial use. I am also using 16-bit DACs for analog signal generating.

I have published many of these sensor interface ideas in EDN and Electronics Design magazines.

I think comparators and latch of LMC555 IC is very interesting one and I will like to use it for over current protection in electrical circuit. It has trigger, reset and over voltage comparator with latch all in one IC.

I think, electronics design is still very challenging one even if engineers are walking on beaten up path. I started all this some 35 years ago and now doing it again for very beginners. It is like teaching your grandchildren, how to stand up and walk.It is still a great fun.

G'day gals, guy, gurus & Shyam,

• "It is not so good to put a lot of power in signals on the Microcontroller board as you never know how many signals one will ever need and which type of signal sense and control one will end up."

As usual your spot on and that's exactly why my designs use BC508 npn transistors to drive the load rather than the output of the microcontroller. The circuit is designed so that no matter what you connect the output to the maximum current it can drive is limited to 100 mA which is well within the BC508 transistors capabilities.

However, I have also designed a second board that utilizes a single TIP32 pnp transistor. This can then drive up to 40 separate devices provided the total current drain is less than 3.0 A.

So, it doesn't matter what you try and use the control board to drive the maximum output current is limited to 100 mA so even with a short to ground you won't damage the board. If you do need to drive more then you just add the power board and connect it to the appropriate output of the control board.

Mind you, all this is only intended for use in scale models to drive things like LEDs and other low power devices. It's definitely not designed to use in highly critical applications or control loops where tight constraints and high frequencies are needed.

However, for the average back yard electronics enthusiast it's hard to go past utilizing microcontrollers. They are cheap, simple to use, extremely versatile and can be programmed to do just about everything your mind can dream up.

Regards, masu

I am planning to change the transistor design to MOSFETs as they have low ON resistance and require much lower driver current from uC I/O pins. Perhaps protected gate and protected source and drain MOSFET are much better than bipolar transistors. Few milli ohms ON resistance looks very attractive.

To save power, I now switch power to sensor and do power management in a program. This can be done using hot-swap MOSFET switches as it is done for the USB port.

Even for relays, two stroke latched relays are much better than continuous current relays.

In my new designs I am planning only 5W or at best 10W power in 5V board power source so a lot of planning to save power and yet use it for tough jobs is planned.

In many projects, I use battery as there are power cuts and sometime experiments are done where there is no chance of mains power. Low power circuits is something I like now and as a rule I avoid high power eating stuffs.

You always end up planning a special use controller design for your application and any general purpose design often used in trial runs or for few applications where there is no chance to redo as requirement is too small so your prototype remains there frozen as final one even though it looks very unprofessional design, but some how it fits in as it works fine for an application..

I have designed uC boards for 3 LCD displays but I do use them for one or two also. There is always a tug of war to select small uC of few pins or big uC having 40 or more pins. Some time you can do things without uC but you do use uC as it looks simple in that way. There is this competition between art of design and just get to the results somehow type designs.

Analog electronics is a real challenge and there is a lot of satisfaction in doing something that looks impossible or real hard to make some sense.

G'day Shyam and others,

I agree and the use of field effect transistors is a far more elegant solution and I thought of utilizing both MOSFEG and JFET transistors but unfortunately the price of them here in Australia would have made the boards extremely expensive to manufacturer.

For example a BC548 costs about AU$0.²⁰ and a TIP32 AU$1.⁷⁵. On the other hand an MPF-102 J‑FET costs AU$1.⁷⁵ and the local store doesn't carry a JFET that could replace the TIP32. When you then go to using MOSFET devices the prices jump to AU$4.⁵⁰ for a VN10KN and AU$6.⁹⁵ for a IRF540.

The other thing that you have to watch out for when using MOSFET and to a slightly lesser extent JFET devices is electrostatic discharge damage. I have actually seen a MOSFET discreet transistor destroyed by a waving a piece of highly charged sticky tape about 10 mm above it and it didn't even come in contact with any part of the transistor.

The problem stems from the way field effect transistors work and as the name suggests they utilize an electric field rather than electric current to activate them. In normal operation the electric field is generated by a couple of volts. When you start waving the 20,000 V static charge you can easily generate by walking across the room the poor old FET hasn't got a hop of coping and because it's the electric field that we are talking about you don't even have to touch the device just get the static charge close enough and

No more FET.

Modern components are less susceptible to ESD but none the less they can be damaged by it and it only takes one uneducated trained monkey, shop assistant or packer to damage the device before you even get it. ESD can also cause a really insidious problem where by it degrades the performance of the device and makes the final circuit more susceptible to noise, thus causing those mongrel intermittent faults that are so difficult to track down and repair.

Don't get me wrong, Field Effect Transistors are definitely the way to go with mass produced electronics where the manufacturer has total control of the components all the way from manufacture to end user. However, for the average back yard shed electronics person there are too many ways that they can be damaged to make them expedient and practical.

Mindy you, I'm going to ignore my own device and use CMOS devices in the next generation of control board, but I will be doing all the work utilizing my ESD field kit like the one shown below.

Actually for any electronic work I recommend purchasing one of these kits and getting used to the idea of working in an ESD safe way whenever handling electronics of any kind. The kit in the image can be purchased for around AU$50.⁰⁰ which isn't much considering it can prevent a board that could cost more than twice that much from being destroyed or worse degraded and prone to intermittent faults.

Anyway, it's time for me to stop waffling and get back into the workshop to practice what I preach so I will say bye bye for now.

Regards, masu

Your explanation may have much more important argument in the High Power and Safety World. Among others I have met "people's" excitement in Smart Grid solutions completely disregarding basic rules of protection and power distribution efficiency and security.

How to make your excellent example of "uneducated monkey" be visible for "law making" and "permit giving" authorities? While law enforcement waits for explosions and death of dozens of workers? Examples: WV coal mine .... to ...BP deep Gulf "experiment" in 2010.

Just a reflexion.

JFET not good for digital circuits, but they are OK as amplifiers for weak signals. MOSFET are better but they are expensive. Unless gate is protected, they may get damaged and you need to remember that they get charged at gate voltage so you have to remove charge. The input scheme differs for MOSFETs.

Motor drivers, H-Bridge in MOSFETs are something worth trying out. They are great in push-pull stage to drive transformer or speaker coil and a lot of load in mini pack. Imagine <10 milli ohms ON resistance of MOSFETs.

G'day gals, guys & gurus,

This is off topic again but it's a classic example of how you should build a prototype before going down the track of designing a PCB.

I was testing out the programming bus that will ultimately be used to program the microcontrollers once they are in situ and inaccessible. The programming bus utilizes a four bit CMOS bidirectional switch that on one side is connected to the microcontroller and the other to the programming bus. Basically when you activate these switches they connect the microcontroller to the programming bus and when they are off they isolate the microcontroller and let it run its program.

Now the microcontrollers only use 5.00 Vdc to operate and the switches can operate on any voltage between 3.00 and 18.00 Vdc so I used the same 5.00 V to supply both the microcontrollers and switches.

However, to set the microcontrollers into program mode you have to apply a voltage of 12.00 V to the V_pp pin on the microcontrollers which is normally supplied from the PICkit2 USB programming unit and negates the need for a second supply voltage on the microcontroller boards. Unfortunately the switches have an inbuilt protection that clamps the voltage on any of the switch inputs/outputs to no more than the supply voltage which in this case clamped the V_pp signal to 5.00 V and thus prevented the microcontrollers from going into programming mode.

Once diagnosed the problem was simply fixed by supplying the CMOS switches with 12 rather than 5 volts. However, this would mean that I would have to supply 12 & 5 V to each of the boards and make the whole thing more complex. I am not 100% certain how I will accommodate this change but at the moment I'm planning on moving the CMOS switches to the board that controls the distribution of power. That would mean I only need to supply each of the microcontroller boards with a single 5.0 V power source and limit the use of 12 V to the power distribution and interface board.

Anyway, it's a classic example of no matter how well you think you have designed something some little oversight can sneak through and prevent your design from working. It also demonstrates how essential it is that you build a prototype utilizing something like a breadboard (see image on right) to test the circuit before you go down the path of designing and fabricating printed circuit boards.

Oh well, masu has to get back to the drawing board so it's bye bye for now.

Regards, masu

Dear Masu

Perhaps a small DC-DC converter, which switches power to 12.0V and from 5V will be ideal. I think there are such regulated and two voltage level small DC-Dc converters that will hardly take space or consume power. You can also use step up charge pump that has gated oscillator. LCDs use this technique as they need more than 5V you apply to them. Like MAX232 makes its own voltages. Charge pump can be very simple and small. Due to high switching frequency, they also provide good regulated high power in small pack if you use inductor and internal MOFET switch of DC-DC converter. I think you know all that and may be already planning to use them. I use some of these to fire APD up to nasty 70V with 1 mA and that is good 70mW power. earlier I was having 500V booster for GM Tubes and 1200V booster for PM Tubes. You never know how high you will go up in voltages.

I think it is more fun these days to have many power supplies made from one and right on the board as they do in your Laptop. You never know what really you may use in selection of ICs and signals. I have ADC ADS7813 which is 5V powered but can take +/-10V at input so switches have to be +/-12V. I used 5V switches and then X2 amplifier at the output of switches. If signal to switches are high then I divide the signal to 1/2 through resistors. I know that switch ON resistance increases when voltages are reduced. There is this trade off.

In critical designs things have to be taken very seriously. One such design is to measure 1fA current. There are instruments that measure 0.1fA so it looks very high but not so high as you may know. I started counting on how many electrons I have and how many thermal noise will eat in its dance and how much that nasty cosmic ray may generate each time it hits the sensing area and so on. Teflon PCB, Teflon capacitors and so on and yet things may go wrong. I always remember Bob Pease for all this and he looks much older than me even though we may be of same age. He used up his brain and hair and wherever he might have found ideas in the body.

I think bio-sensor electronics is most challenging one. Sensing molecules and discriminating then by signals is real fun. Imitating our nose is not so easy but I will like to go beyond. People will sure go beyond. It is just a beginning of understanding of natural circuits to what we make in crude way out. Yes, most of our work is very crude and primitive and it will be refined to very high level in only decades to come. Unless world comes to an end, there will be lot more developments and at much faster rate.

One good reason for me to encourage young people is just that they are the future for the world.

G'day Shyam & others,

Using DC-DC converters is a good idea and I had a look at the local electronics store but the only ones they had were huge high current devices that were way, say, say to big. However, I've been playing about with the circuit on my breadboard and I'm pretty sure how I am going to do it. The image below shows a block overview of the way it all hangs together.

Each of the Control Boards μCB (green squares A, B, C & D) is connected back to the Power Distribution & Program Interface or PDPI board (faun rectangle in the middle near the bottom) via ribbon cables (light grey cables). This supplies each of the control boards with the 5.00 V they need to run and the signal lines needed to program the microcontroller chips.

The PDPI board not only supplies the 5.00 V needed for normal operation but contains the bidirectional switches that connect/isolate the microcontrollers and programming bus.

The 5.00 V needed for normal operation is supplied to the PDPI board via four bloomed stainless steel cables (black & red lines at the top left) that also suspend the model. These should not only be strong enough to bear the weight and supply the power but should be fairly difficult to see.

When the μCB are programmed a specially made cable is plugged into the Programming Port (Orange Rectangle at the bottom right). This supplies both the 12.00 V V_PP needed to program the microcontrollers and the four signal lines that are used to carry out the programming.

Which μCB is to be programmed is selected by placing a magnet on the outside of hull in the proximity of the μCB being programmed. This operates a reed switch on the board which then sends a signal from the μCB to the PDPI board where it activates the appropriate bidirectional switch connecting it to the PICkit2 programmer.

This limits the number of places that cables have to penetrate the hull to the four needed to suspend the model and supply the power and the multi pin connector for programming. In normal operation the programming cable will not be connected and the hole concealed with a small cover.

So far the most suitable connector I can find, are relatively inexpensive, available and small enough to conceal Binder Series 711 Sub‑miniature Circular connectors like those shown in the image on the right. The female connector (upper image) will be mounted so it is slightly recessed from the hull. It will then be concealed by inserting a small cap that covers and conceals the connector when it's not being used for programming.

Mind you, that's version 5-42 so there could very easily be a version 5-43 if I find a better way of doing it.

Regards, masu

Dear Masu,

I think you are on right track.

Recently I switched to 24V distribution power and use regulators on board and this gives a lot of flexibility and lower current in the power line. One simple reason is that 24V is almost industry standard.

Most of the DC-DC converters, relays are available for 24V input. Only few DC-Dc converters are designed for 12V and 5V. 48V power source is still not very popular so i am keeping out of it. Transistors function better with higher voltage and lower currents if you compare 5V and 24V rails.

Whatever is your plans sure are very thoughtful and you should go ahead in that direction.

I think Coto Relays are the best with life of 100 million to 1 billion operations. You can also PCB mount them. I use them for avionics and nuclear electronics. You can switch many signals from one relay and are excellent for bus switching.

DC-DC isolation is another greater concern for me and 4kV isolation is the minimum I use. Relays give 1kV to 4kV isolation, opto couplers give 5kV to 40kV isolation.

I think FRAMs are good for storing programs and are very fast and need no power to retain data. See www.ramtron.com for details. They even have state saver for LOGIC signals.

Your armored cable idea is attractive one. I am strugling to get multiple pin connector that has 3kV or 5kV isolation and pin can carry 5A to 10A current. Not all signal lines are for high current but some are nasty power eaters and are also at high voltage bias.

I use standard 2U height 19" rack module for inserting all these hardware. I may also use 3U and 4U in coming months.

See how these hardware look like. They have BNC like SHV connectors for 15kV.

uC boards go inside for all house keeping jobs. Some of these are RS232 interfaced. Many of these having different functions are placed into a single system. It does not matter what they do, as each module does something special. This one is 15kV Supply.

Try to draw a diagram.

Most "amateurs" will understand better your circuit idea.

Forgive me if I appear to be stating the obvious, but you do realise that the strip board layout is a view on the underside of the components? On the stripboard layout pin 1 is on the top left of the diagram.

"the strip board layout is a view on the underside of the components"

Eh, what? Yes pin 1 is the upper left pin of the 555 on the strip board layout but that's from the top of the chip not the underside.

I think they should designate all the pins as Pin 1. Sure'd spare folks a lot of confusion. :-)

Hi its me the guy who originally asked the question.

I regret to inform you i made a very very stupid mistake in laying down my circuit.

I have built the timer circuit (did a different design from one of the ones suggested), using a LED to test the time i get 50 seconds, however when i attach my motor to the circuit itself or even using the 2N3055 transistor, the timer doesn't last more than 6 seconds or so.

I do not know what is wrong as when i take the motor off and just have the LED it runs just fine back to 50 seconds.

I am only using the 1 power source for both the timer and the motor, is that a problem?

Keep them coming, I love this sort of thing!

This sounds like you have the motor connected to the timing inputs rather than the output of the 555.

1. How are you using the 2N3055 to drive the motor?
2. Can you post a diagram of the circuit you used?
3. Do you know how much current you motor draws when running?

The transistor you are using can drive a 15 A load but it doesn't have a really high current gain and depending on the sort of current the motor you are using draws may not be driving to motor properly. The current gain of the 2N3055 is somewhere between 20 and 70 and the maximum current the 555 can supply may be as low as 100 mA. That means that the maximum current that the transistor will drive may be as low as 2 A. You may need to introduce a second smaller transistor to get the sort of gain that you need to drive to motor. Unfortunately there is no way to know without knowing the current that the motor actually draws.

If you have access to a multi meter it would be really helpful if you could find out how much current the motor you are using actually draws. To measure this connect the meter, motor and power supply as shown in the diagram.

Make sure that you watch closely as you turn the motor on as there will be a surge in the current as it starts to rotate. It will then drop down to a steady state. We need to know how much current the motor draws both when it has settled down as well as the maximum current as the motor starts.

To be certain of what is going on we really do need all this information plus the circuit diagram. Without it we are only guessing.

I would also suggest becoming a member of CR4, it doesn't cost anything and we know who we are talking to.

YES masu!

To know what is the value of the current, do measure it using the simple connection shown on your diagram.

To experimenter: Be sure that the Meter + & - are meter terminals for Amps (DC current) that are many of the time different that the others applied to voltage measurements.

Said you would read 6.22 A as a current at 12 V in steady state (running at full required speed and mechanical load if any). You must multiply by 3 to 10 (as advised above) to get a starting value at speed zero rpm. Suggested transistor output current for its selection = 62.2 A. Unbelieved? It will delivered just for short time. of course.

But...You may also measure the starting - locked rotor current with the recording current device that will record this current just immediately after switching ON. This will assure its true value (mostly lower then 62.2 A) This true value lets avoid overestimating.

The other solution to measure this starting current is to lock mechanically (so not let run) the motor shaft and measure this current but it must be done fast (in very short time) to avoid the motor winding burn out. Again better is to have a meter with ability to fast recording. If you have access to electrical laboratory, they maybe have it.

Something I had forgotten about, it's a long time since I studied motor theory, was that a motor can be approximated circuit wise as a resistor in series with a voltage source. The resistor represents the resistance in the windings and the voltage source represents the back EMF caused by the rotation of the motor.

You can calculate the value of the resistor by measuring the resistance across the terminals of the motor with a multimeter while slowly rotating the motor by hand. The lowest value that you read will be the resistance in the windings of the motor.

You can then use Ohm's law to calculate the peak start current that the motor will draw as follows.

Current_Start = Voltage_Supply ÷ Resistance_DC

This will give you the peak startup current, however, this is the absolute maximum current that the motor will draw and only lasts a very short period of time.

Yes, so we have now three ways to estimate starting (locked rotor) motor current.

If DC motor has brushes, we may have (maybe neglected) some errors. R brushes is nonlinear, its value is also function of the voltage so it is possible the measured total R by Ohmmeter (small battery voltage) will be different that the one existing in the motor at its full supply voltage (-EMF). Test for motor locked rotor Resistance is done mostly under lower voltage to avoid motor current (Device Under Test = DUT) exceed its nominal rated value.

You are right that motor current calculated from measured total motor Resistance can be applied to select the transistor. It can be assumed to be "max - worse case scenario value" at Emitter / or collector/ transistor terminal.

Locked rotor current is exponentially decreasing according to inductance and dynamics of the motor to the value necessary to run its mechanical load.

I do not think it is all about dynamic theory of electrical machinery but some light could be helpful for the students writing papers or filling lab reports.

I couldn't agree more that you should sign in and become a member, I just repaired my own small circuit board from this. This board with a negative feed it drive a dc motor and I am not an electronic person. Check your 2N3055 transister to drive dc motor, I use NTE transister with 800V./25A. with K, A, G pin. Good luck.

You have convinced me to register, ill give you all a sit rep.

After building my timer circuit, i got 50 second with a led - perfect!

After attaching motors (to the transistor) to this it lasted 3-6 seconds, there are a couple of possibilities for this, one being it chewing up the batteries and destablising the power through the 555.

After taking some advice form a lecturer (who looked at me in disgust for using a 555 timer for motor control), and an e-friend; I have abandon using a transistor for the power control, as i just want to give it all i have got! I am going to use a low power 3 terminal 5 volt power regulator (LM109) to maintain the voltage across the 555, then using a 3 volt activated relay from the output of the 555 to control it, to power the motors, and attaching a 1nF capacitor to help start the motors.

I understand using a transistor for higher power/current items, but as this is so low with such a massively overspec'ed transistor i have the feeling it isn't too much use. As i do want the most simple solution (power to motors) i think the relay s the best option as opposed to using a transistor to 'amplify' the signal.

If I remember correctly the time base of the 555 is supply voltage independent. That means if your motor is not pulling the supply voltage down below 4.5 V then there should be no change in the timing of the output. So if you power supply can run the motor the only answer it that when you connect the motor you are some how changing the value of the input to the 555.

I think what is happening is you are connecting the motor drive transistor to the input terminal rather than the output terminal. If you have a LED connected to pin 2 you will see it go on and off as expected but as soon as you connect the motor you will severely change the time base.

Are you absolutely sure that you have the motor drive circuit connected to pin 3 of the 555?

Go to this website and see: http://www.circuit-innovations.co.uk/555.html. Good Luck.

Is it possible to Cut & Paste the 555timer diagram and add the Power Transistor symbol with motor terminals protected by reverse biased diode? The link is perfect just for 555 because has diagrams. Each discussion on this kind of problem should start with a diagram

Hi southern123,

"Is it possible to Cut & Paste the 555timer diagram and add the Power Transistor symbol with motor terminals protected by reverse biased diode?"

The short answer is no but if you need a circuit I can draw one for you and email it to you.

I use a drafting package called DeltaCad. It's a simple drafting package that I use to create all sorts of drawings including plans, circuit diagrams, printed circuit boards, technical drawings and the diagrams I post at CR4. It is not a design package but rather a 2D drawing package. If you have had any technical drawing training it will take you a couple of hours to do the tutorial that comes with it and become reasonably proficient. Best of all is you can get a demo copy from their web site and a full license is only a one off payment of US$39-95. I have been using it for over ten years and for personal use it is hard to beat. You can also save your drawings in formats that packages like AutoCAD can read.

Thank YOU masu!

You saved me some frustration to try invent-build-into wheels.

What you think about sketching > scanning > attach a diagram to text in CR4?

I believe I should pay you!!!. Or ask to visit some pub for a friendly cup of byeaar (is it Aussie bear? My teacher told me)

Hi southern123.

If you wish to insert an image in a CR4 post, all you need to do is click on the image button in the editor toolbar. The image on the right shows the image button. The tool bar is directly above the text insertion area.

1. Click the Image Control When you click the image control tool a pop up window will appear with some text boxes and control buttons.
2. Select the Image You need to either insert the URL for the image you wish to insert or click the Browse button. The browse button allows you to browse the files on your computer to locate the image you wish to insert.
3. Select Alignment The next text box is optional and sets how the image is inserted in the post. You can align the image to the left, right or leave this field blank. If you leave the field blank the image will not be aligned and will show text before and after the image but not adjacent to the image.
4. Submit Image Once you have completed the previous steps clicking the Submit button places the image in the editors text window.
5. Resize and position the Image The image will appear at the beginning of any text you have already typed. You can now drag the image to where you wish it to appear in the post. You can also resize the image by dragging a corner or edge.

Depending the speed of you internet link it may take time to load the image and BMP format are the slowest to load. Compressed files like GIF or JPG take considerably less time to load.

Have fun inserting images.

Free download for your pcb drawing. http://www.pad2pad.com/demo/index.htm Let me know if this help you. Good Luck