Display 4-20 mA on LED Display

Just about any 8bit microcontroller with enough I/O pins to dive an LCD display or a serial diplay will do it, (eg Z86E08 would be big enough) but you need to be able to write assembler and design the circuit to implement an A to D converter. Ypu also need a development/emulator board.
It's beyond the scope of a simple post to teach you electronics and assembler programming in a single post.
Do you have any electronics expertise, are you a hobyist or do you know nothing about electronics?
Del

3

Hi again

Sorry I did not write that I want the circuit to be build with IC's. I think it should be possible, I have seen the layout some time ago, but I can't remember how it was designed.

And yes I have some electronics expertise (B.Sc. Electrical but specialized in Power Engineering), but this board I will use as a hobyist.

I will be glad if someone could help me with the design.

Regards

Jkp_Lab

Electrical is NOT electronics.
You can probably buy a module which will do it.
Designing and builing from scratch isn't easy.
I'd suggest you learn to use microprocessors, there are kits for the PIC series and loads of data and circuits for them.
But if you are starting on as an electronics hobyist I'd suggest something simpler like a series regualted power supply, or maybe just play with comparators (or OP amps which will do the same).
A series of comparators with LED outputs would make a simple 4-20mA monitoring device.

Del

As Del suggested there are both finished modules and kits, or you could just buy a cheap voltmeter and select the milliampere scale you want etc.....expect to pay less that $10 for a cheap one.......

If you want to build one in, buy a finished module.....it will cost maybe $20 or so. To measure milliamps, you measure the voltage developed across a shunt resistance. Just apply Ohm's Law...

Somewhere like this may have what you want as a kit:-

Ramsey Electronics

To measure milliamps, you measure the voltage developed across a shunt resistance.

I would suggest a different way to measure: the heating effect on a resistor when current passes through it.

The answer depends on how much time and money you want to spend. As stated, there are modules that you can purchase to do this.

Options:

1) buy the smallest and cheapest digital multimeter you can find, remove the casing and mount it to your circuit board. You should be able to pick one up for under $10.00 (cheaper than running around and buying all the parts). Use a voltage regulator IC to bring the voltage down from 24VDC to 10 volts LM7810 or you can use a zener diode or a resistor voltage divider.

2) use a microcontroller

3) construct the circuit yourself using op amps. There are lots of circuits on the internet using op amps or A To D converters and LED's.

Option one is the quick and easy way. In fact, with the price of multimeter so low, you can use them for just about any project that requires measuring voltage, current, frequency (below 300 Hz). As long as you only need to display the information, just stick one in a box of you own design and you an accurate inexpensive device with a display. Add a selector switch and you can use it to display 3 phases of voltage or current.

Hi to all of you

Thanks for all your suggestions, I know there is a lot of easy ways to solve my little issue, and using and ordinary multimeter is the most obvious solution. But the thing is that I'm developing an prototype print, that shall be used together with some other electronic circuits, on one print.

If any of you could help me with a IC print circuit that could solve my problem, or just a link to a web-side where I can find the solution, I would be very pleased. I have already been surfing the net before I asked the question inhere, but I was not able to find a proper solution event though I found some pre-manufactured circuits.

I know that my solution with IC isn't the cheapest way to solve the problem, but I think that this is the best solution to fit my print circuit.

Regards

jkp_Lab

Hi, how about an old fashioned analog display, the ones with a pointer which goes from one side to another when voltage changes??

For example, you can change the 4-20 mA signal with a 500 Ohm resistor to 2-10 Volt measured across. And you can take out the paper behind the pointer and make your own scale.

Regards, moe

ICL7106 or ICL7107, about $4.00 at Digikey

Beka Instruments (usual disclaimer) already sell a number of devices that can do this task, most of them even approved for use within Ex i circuits.

just buy a digital ammeter, disassemble it, and then transfer it to your desired pcb.

I'm also into costum electronic circuits designs,,, we can exchange ideas through yahoo messenger, my ad is katakawan2008@yahoo.com I'll be glad to discuss with you there about your ideas and mine on electronics tech..

Hi jkp_Lab,

You might be able to use this:

OEM 1B-LED

8mm (0.31") Digit Height 200mV Full Scale Reading Auto-zero and Auto-polarity Selectable Decimal Points DIL Pin Connection

This low cost sub-miniature LED voltmeter module is ideally suited for high volume applications. It features an exceptionally large display in a miniature package and includes auto-zero and user-selectable decimal points. The use of low current display technology means this LED product can be considered for battery powered applications. The OEM 1B-LED is dimensionally compatible with its LCD counterpart, the OEM 1B. Connection to the module is via two rows of pins. This is a popular part, normally stocked in high quantity and suitable for new designs.

It can also be used as an ammeter:

http://www.lascarelectronics.com/pdf-usb-datalogging/data-logger0931654001208960858.pdf

They list the price as $27.20 for one, but I have gotten them elsewhere for ~ $15.00 (Digi-Key, but they no longer carry them) - you may have to look around.

Mike