Sites: GlobalSpec.com | GlobalSpec Electronics | CR4 | Electronics360
Login | Register
The Engineer's Place for News and Discussion®

Previous in Forum: Amateur Radio Satellites   Next in Forum: Mobile Charger
Close

Comments Format:






Close

Subscribe to Discussion:

CR4 allows you to "subscribe" to a discussion
so that you can be notified of new comments to
the discussion via email.

Close

Rating Vote:







22 comments
Commentator
Engineering Fields - Automotive Engineering - Race ya there... Engineering Fields - Mechanical Engineering - Take everything apart, and while you're in there... Engineering Fields - Manufacturing Engineering - Metal, Metal, Everywhere. United States - Member - Good ole' USA.

Join Date: Jun 2006
Location: Orlando, FL
Posts: 82

Voltage Sensor to Computer Interface

03/19/2007 6:35 PM

I'm working on creating a sensor-to-computer interface for an automobile, (and subsequently a computer-to-peripheral interface.) My aim is to replace the in-car "ECU" with a PC (most likely Linux-based) for full control over fuel curves, spark timing, etc. Problem is, although I've had a little experience with designing and building circuits, I've never dealt with anything of this difficulty, and don't know where to begin. I'm assuming I'll need a programmable microprocessor to do all the dirty work, but aside from that, i'm fairly clueless.

I'm pretty much looking for anything here - first hand knowledge and help or just good books or websites to read. Thanks.

__________________
I reserve the right to be wrong, or of no help what so ever - Del The Cat
Register to Reply
Pathfinder Tags: automotive car circuit computer microprocessor schematic
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.
Guru
Engineering Fields - Electrical Engineering - New Member

Join Date: Sep 2006
Location: El Lago, Texas, USA
Posts: 2612
Good Answers: 64
#1

Re: Voltage Sensor to Computer Interface

03/20/2007 10:35 AM

There's quite a bit of ECU / PC info out there - google is your friend.

Register to Reply
Guru
Technical Fields - Architecture - New Member Popular Science - Weaponology - New Member Engineering Fields - Control Engineering - New Member Engineering Fields - Electrical Engineering - New Member Engineering Fields - Electromechanical Engineering - New Member Hobbies - Fishing - New Member Hobbies - Target Shooting - New Member Hobbies - Hunting - New Member

Join Date: Dec 2005
Location: Clemson, South Carolina
Posts: 1746
Good Answers: 20
#2

Re: Voltage Sensor to Computer Interface

03/20/2007 2:38 PM

You're kidding -- right? Auto manufacturers have had systems for many, many years to do just what you want to do, and they had 100's of engineers as a resource and I expect they invested 1000's of man-hours. What they didn't do was give you a socket for a laptop plug. And you expect to get simple answers to complicated questions from this forum? Shame on you! Also, how the heck do you expect to accomplish your goal if you don't have much experience designing and building circuits? I've been designing and building circuits for over 25 years, and I don't know that I would know everything I need to know to do such a thing.

However, there are third party outfits which make diagnostic equipment to plug into an automobile's computer/sensor network. Maybe you can modify/reverse-engineer one of those to figure out what's what.

As far as engine performance or efficiency is concerned, try looking up stuff on the internet about high-performance engines. A by-product of learning how to squeeze HP out of a gasoline engine is learning where the efficiency curve reaches a maxima.

Good Luck!

__________________
We have met the enemy and he is us . . . Walt Kelly
Register to Reply
Commentator
Engineering Fields - Automotive Engineering - Race ya there... Engineering Fields - Mechanical Engineering - Take everything apart, and while you're in there... Engineering Fields - Manufacturing Engineering - Metal, Metal, Everywhere. United States - Member - Good ole' USA.

Join Date: Jun 2006
Location: Orlando, FL
Posts: 82
#3
In reply to #2

Re: Voltage Sensor to Computer Interface

03/20/2007 3:01 PM

Thank you for telling me what I want to do. I already know what I want to do, since that's the first step in planning. The second step is getting the information, something you haven't helped me at all with. I understand my limitations, handicaps and abilities better than anyone else I know, and therefore do not need a consult on what I can and cannot accomplish.


Being an automotive "enthusiast" to say the least, I have plenty of knowledge about the existence of aftermarket ECU tuners. These are designed to plug into the OBD port on a vehicle and examine or alter the behavior of the ECU itself, the part I want to eliminate. The ECU is a cost effective miniaturization and simplification of an overall controlling computer (built by the lowest bidder, i might add) and therefore has limitations inherent in the design, from the get-go. What I want to accomplish is much bigger, much bulkier, and orders of magnitude more customizable than what is currently installed in vehicles from the factory. The main reason is that 95% of automobile consumers DO NOT NEED what I want to do.

__________________
I reserve the right to be wrong, or of no help what so ever - Del The Cat
Register to Reply
Guru
Technical Fields - Architecture - New Member Popular Science - Weaponology - New Member Engineering Fields - Control Engineering - New Member Engineering Fields - Electrical Engineering - New Member Engineering Fields - Electromechanical Engineering - New Member Hobbies - Fishing - New Member Hobbies - Target Shooting - New Member Hobbies - Hunting - New Member

Join Date: Dec 2005
Location: Clemson, South Carolina
Posts: 1746
Good Answers: 20
#4
In reply to #3

Re: Voltage Sensor to Computer Interface

03/20/2007 3:26 PM

Pardon me, but I don't see in my post where I told you what you want to do, nor did I tell you what you can or can't accomplish. I think you may have jumped to the erroneous conclusion that I think you're an idiot . . .

What specific information do you want?

Bhankiii's comment, "There's quite a bit of ECU / PC info out there - google is your friend." Pretty much says it all.

__________________
We have met the enemy and he is us . . . Walt Kelly
Register to Reply
Active Contributor

Join Date: Feb 2007
Posts: 13
#15
In reply to #4

Re: Voltage Sensor to Computer Interface

03/21/2007 8:56 AM

Well done Bill! You sign on as a power user, but I think power-abuser would be more to the point.

If everyone responded like you do, these forums would be useless as no-one would ever risk asking questions.

Perhaps it hadn't occurred to you that the reason you couldn't do it after 25 years work is because you're not open minded enough.

Good luck to Phoenyx, the difficulty of the task is no reason for not doing it.

As for me, the lack of a formal qualification or years of experience has never stopped me doing anything. I left school at sixteen, I've worked as a builder, a photographer and I've just designed a spectrometer that measures blood oxygen saturation in a heart catheter.

Consider yourself duly chastised!

Andrew Holder

Register to Reply
Guru

Join Date: Dec 2005
Location: Wisconsin USA
Posts: 849
Good Answers: 37
#5

Re: Voltage Sensor to Computer Interface

03/20/2007 8:38 PM

I'm pretty much looking for anything here -good books or websites to read.

Here's one site to check: http://www.perfectpower.com/products/smt6.asp

Without knowing your actual needs, it's tough to get specific. However, the mechanical aspects and time constants of the engine and its systems may set a practical limit to how much gain can be obtained even from "full control over fuel curves, spark timing, etc. ". That's one of the reasons that "lowest bidder" built controls are usually adequate, even if aftermarket chips can wring out more horsepower & torque. The low-hanging fruit (i.e., big gains for the buck or the level of complexity) is long harvested, and you're into gleanings. But, if you're going to run exotic fuel, heavily modify the engine itself, or otherwise depart from the norm, full control can become desireable again.

__________________
" Ignorance and arrogance have more in common than their last four letters. "
Register to Reply
Guru
Hobbies - HAM Radio - New Member United Kingdom - Big Ben - New Member Fans of Old Computers - Altair 8800 - New Member Canada - Member - New Member

Join Date: Jun 2006
Location: Toronto
Posts: 3576
Good Answers: 95
#7
In reply to #5

Re: Voltage Sensor to Computer Interface

03/20/2007 9:24 PM

as someone say, it has been done. Some cars have an accessible part you can remove and program to do what you want. Others give you no access to the intricacies of what goes on...they are cheaper to make as a sealed unit.

In any event drill these.

http://www.google.com/search?hl=en&q=%22engine+computer%22+%2Bmodification

http://www.google.com/search?hl=en&q=%22engine+computer%22+%2Bmodding

__________________
Per Ardua Ad Astra
Register to Reply
Anonymous Poster
#6

Re: Voltage Sensor to Computer Interface

03/20/2007 9:07 PM

SMT6, Megasquirt

Reason for piggy backing is to retain OEM functions like A/C, cruse control, ABS, gauges, warning lights etc. Unless you could find a way to interface all the system with your PC/ECU, you'll need the stock one. Oh removing OBDII from the car should be illegal unless you're building a track only car. In that case this is not the place for you.

To read sensor data into any computer you'll need Analogue to Digital converter. You'll also need a set of I/O to control relay to activate different system. Every sensor have different signal, voltage, current, resistance, pulse, inductive, capacitive etc.

With what you said here, you have a long way to go. You have absolutely no clue on how to do it. How much do you know about real time programming? Assembly language? AD conversion rate? How fast you need to read and respond to sensor reading when the engine is running at 6000RPM?

Why reinvent the wheel when you can buy one off the shelf?

Pineapple

Register to Reply
Power-User

Join Date: Sep 2006
Location: New Jersey, USA
Posts: 166
Good Answers: 7
#13
In reply to #6

Re: Voltage Sensor to Computer Interface

03/21/2007 6:15 AM

Some newer cars, maybe even a lot - not sure, use a BCM in conjunction with a PCM. They are 2 seperate computers the BCM - Body Control Module, deals with a lot of the more mundane body functions like HVAC, alarms, windows, etc. The PCM - Powertrain Control module is usually reserved for the engine and related. These are GM terms and other manufacturers may use different acronyms. This is not to discount your point at all pineapple as it is a very good one. In addition to the obvious controls the PC would have to handle on a modern car you would probably want/need to reproduce the bus be it OBD or Can bus which may or may not go to the guage pod, the radio, the HVAC, etc.

To make something like this a bit easier to start I would suggest trying it on an older car, maybe even one without a computer as it will be a lot easier to interface into the car then trying to replace something that is so embedded in the modern automobile.

Shawn

Register to Reply
Power-User

Join Date: Dec 2005
Posts: 200
Good Answers: 8
#8

Re: Voltage Sensor to Computer Interface

03/20/2007 10:11 PM

Phoenix, Listen to all the agenda propaganda and die. A circuit designer with no credits. Auto experts easily offended. Move on.

The auto engine is very simple. Each cylinder needs to fire a spark plug precisely at 40K to 100K volts a tunable 0-10 degrees before top dead center. End of discussion. There is plenty of room for improvement. A shade tree can do this by "ear" with no war.

PC lockout blackout benefits major corporations, GM, Ford at the expense of Joe Smith. I take my Ford to the Ford dealer and get less performance afterwards than before. The Ford Techs can not do a simple tuning job at $600 per throw on a Ford product. Ford Techs can not even read the codes. Sears has products that will read and decode any problem. Ford techs can not do simple ignition tuning. All they know how to do is replace spark plugs and perhaps with extreme difficulty, replace spark plug wires. Last week a Ford dealer said point blank he did not know how to replace the spark plugs on my Ford. Complete failure on your part will be an improvement over the existing options.

Thus you get all these "Experts" with "discouraging words". Because the self proclaimed experts fail, they want you to quit. Go for it. Start by simply designing a PC screen that allows any PC owner to tune his own auto by adjusting the TDC, trouble shooting wire and plug resistance. Be sure to jump through the legal loops. All the Experts will be watching with agenda to stop your efforts. They make a good greedy fortune trying to prove no one can do it.

Except for the spark plug performance, All electrical items on the vehicle are for convenience except precisely tunable repeatable reliable delivery of spark to each plug. Leave as is the Wipers, lights, radio, cd, lighter, blinkers. Concentrate on spark plug firing, tuning, and adjustment.

__________________
Corn Stoves
Register to Reply
Commentator

Join Date: Sep 2006
Posts: 76
#9
In reply to #8

Re: Voltage Sensor to Computer Interface

03/21/2007 12:10 AM

Cornstoves

At the risk of oversimplifying, your response to Phoenix is...inadequate. First, a disclaimer. I have no automotive engineering credentials, and only enough knowledge to get myself deeply in trouble so there will be little point in attacking me. Nevertheless, I will chime in with an opinion and a thought or two for Phoenix to consider.

Internal combustion engines are in fact quite simple. You are correct in that regard. Optimising the performance of one is another question altogether. There is an awful lot more than just spark timing that is controlled by the ECU in a modern automobile. I'm not speaking of peripherals. I'm thinking of fuel pressure, mixture, and injection timing. These are commonly controlled in a dynamic way as well as ignition retardation under load and even, I believe, in some engines, valve sequencing and timing. The engines I grew up with accomplished many of these functions with mechanical cams and levers and each adjustment was a compromise chosen to fit the engines operating curves. Now the ECU looks at the engines operating parameters and adjusts them continuously.

Phoenix, it seems to me that you have a fairly steep learning curve in front of you but it is entirely doable. The guys that invented and engineered these things are no smarter than yourself--they just have a lot of time (probably a major portion of their lives, if they are qualified engineers) invested in learning the necessary skills. If you are to be condemned for anything, it would be not having done enough homework before approaching this forum. It seems to me that all the information you need is likely available on the web. The difficulty is in educating one's self enough to ask explicit and relevant questions. The links you were given will be a good place to start. When you approach this forum with those kinds of queries you will probably obtain input from some very smart and experienced individuals--and some who have a very high opinion of themselves whether or not they have credentials to back it up. Doesn't matter--all input is useful in either a positive or negative way.

It would seem to me to be reasonable to start by identifying each available control circuit on the particular engine you have chosen as a test bed. There will be an oxygen sensor to control the mix. There will be an air intake sensor involved also. There will be several sensors and controls involved with the various aspects of spark duration and ignition timing. These all will use rpm and vacuum data as well as input perhaps from the transmission. All the temperature stuff from intake and exhaust manifolds as well as water jacket temps may or may not be sensed and input on your particular engine. These represent some of the external considerations.

Next, you will have to get on top of the intricacies of the ECU operating system having to do with jargon like I/O, RAM, ROM, CPU speed, clock speed, etc. When you understand all of that, your next task will probably be to duplicate it with your external unit. Once you have accomplished that, then you are ready to try to improve on it. In my opinion, you will probably discover that, given the mechanical limitations of your chosen test bed engine, the improvements you can obtain are indeed only "gleanings". Then you will be faced with the decision of whether or not it is worth the effort to make the mechanical mods that would allow you to go further.

Bottom line is simply that you cannot improve on something until you understand why it is the way it is. There is certainly no reason not to make the attempt however. It seems to me that the accomplishment of this project--even if you discover that no significant improvement can be made--would be of great personal satisfaction nevertheless. Much luck and good wishes in your endeavor.

Lonnie

Register to Reply
Commentator
Engineering Fields - Automotive Engineering - Race ya there... Engineering Fields - Mechanical Engineering - Take everything apart, and while you're in there... Engineering Fields - Manufacturing Engineering - Metal, Metal, Everywhere. United States - Member - Good ole' USA.

Join Date: Jun 2006
Location: Orlando, FL
Posts: 82
#20
In reply to #9

Re: Voltage Sensor to Computer Interface

03/21/2007 2:47 PM

Thanks for the clarification, and definitely thanks to all of you who are backing me up on this instead of just nay-saying. I didn't particularly feel it necessary to post my resume on here just for a simple question, but to reassure the positive-attitude crowd that I seem to have gathered, though I'm not expert in any one area, I do have a very broad background with which to use as a nice foundation. I was introduced to my first computer at 6, started programming at around 8 or 9, and messing with circuitry and electronics about the same time. My grandfather was an electronics repairman, and he helped and encouraged my learning. My dad was a mechanic for a long time with his own shop, and encouraged my mechanical aptitude. I got my first car at 16 and by the time I graduated high school I was already rebuilding engines and (correctly!) modifying, repairing and upgrading chassis electrical systems. I have a natural ability to learn very quickly the subjects that interest me. I can pick up skills extremely fast. I understand the concepts and theory behind many things, electronics and mechanics especially, and all it takes to turn those into practical skills and applicable, working knowledge is a little bit of hands on time. So when the nay-sayers say that the Average Joe lacks the skill to do something, tell Joe. I'm David.

Oh shit. Now I sound egotistical.

__________________
I reserve the right to be wrong, or of no help what so ever - Del The Cat
Register to Reply
Associate

Join Date: Jan 2007
Location: Edmonton, Alberta, Canada
Posts: 48
#10

Re: Voltage Sensor to Computer Interface

03/21/2007 1:39 AM
Register to Reply
Guru

Join Date: Aug 2006
Posts: 4542
Good Answers: 246
#11

Re: Voltage Sensor to Computer Interface

03/21/2007 2:29 AM

Lots of naysayers here, aren't there?

If I were in your shoes, I'd start with a relatively simple car (a subcompact 1990 model for example). You might end up destroying parts of the wiring harness to get the various plugs and sockets required to make your connections, and may blow out a couple electronic devices in the process as well -- so for this first "proof-of-concept" project, having a car that you can treat as expendable would be a good thing.

Bosch's Automotive Handbook is an excellent resource that will tell you a lot about various injection systems and ECUs. They've published several other books on injection systems and ECU's which would be useful after you've digested the Automotive Handbook.

Once you understand the nature of the sensors, then you can look for suppliers of the a/d converters required. You'll want to research, early on, whether your system will have sufficient processing power for the task -- you may find that all the overhead of the operating system and drivers for converters, etc. may mean that your system won't be able to keep up with the engine. Last time I checked, a PC used as an oscilloscope makes a pretty poor oscilloscope -- generally, purpose-built hardware is much faster than general-purpose hardware.

If all you want to gain control over is the fuel curves and ignition timing, there are already accessory ECU's that allow you to do that. All of these are not legal for use on the road, of course, nor would your system be. Some of the racing ECUs use a laptop for programming purposes, but not for handling any real-time computations. Many of the latest OE ECUs are flash programmable at the dealership level.

Sounds like an educational project and a phenomenal challenge. I'd guess just the I/O adapters alone would cost more that a programmable ECU, so this will not be an inexpensive undertaking. The thought of actually having a car run routinely on a laptop would be pretty unnerving -- if my car's ECU were as unreliable as my PC, I would have long ago decided to walk everywhere.

The wikipedia article on ECUs has some good info and links: http://en.wikipedia.org/wiki/Engine_Control_Unit

Do you have anything in mind for this project beyond self-education?

__________________
There is more to life than just eating mice.
Register to Reply
Guru

Join Date: Aug 2005
Location: Hemel Hempstead, UK
Posts: 3290
Good Answers: 155
#12

Re: Voltage Sensor to Computer Interface

03/21/2007 4:37 AM

Hi Phoenix,

I was going to start by copying Lonnie's (Ishurtle) disclaimer, but, then I read his post and realised he knew vastly more than me about automotive engineering. Still for my two penneth:

1.) You could start by looking at a good automotive DMM.

2.) As other people have pointed out: your biggest problem is going to be getting your PC to run real time "enough": here's an article on real time Linux http://www.linuxdevices.com/articles/AT4503827066.html

3.) You may end up with a scheme that dynamically swaps out the address space in an existing ECU.

__________________
We are alone in the universe, or, we are not. Either way it's incredible... Adapted from R. Buckminster Fuller/Arthur C. Clarke
Register to Reply
Anonymous Poster
#14

Re: Voltage Sensor to Computer Interface

03/21/2007 8:29 AM

Three companies we have used for vehicle communications are Intrepid Designs (NeoVI), Dearborn Group and Vector Engineering. They all make computer to vehicle bus interfaces. You can write your own software to control the remote devices and simulate / replace the components if you know what you are doing.

Make sure you are not working on a vehicle with a passenger air bag deployment system. The vehicle needs to periodically communicate with the ECU on the seat to control air bag deployment. Typically these have indicator lights to let you know if the passenger side air bag is enabled or disabled.

Register to Reply
Participant

Join Date: Mar 2007
Posts: 3
#16

Re: Voltage Sensor to Computer Interface

03/21/2007 11:18 AM

I thiknk you are trying to redesign the wheel here. There are several companies that already have products that do exactly what you are trying to do. AEM (Advanced Engine Management) http://www.aempower.com is my choice. From your post is seems you have more knowledge on the theory of an internal combustion engine than the application and design of a highly complex computer system. Stick with what you know!

Register to Reply
Anonymous Poster
#17

Re: Voltage Sensor to Computer Interface

03/21/2007 12:37 PM

I'm no auto engineer, that would be nice. I just tune my car and build the engine as hobby. I also build PC IO and A/D card on ISA bus for fun. I'm adding A/D and flash memory to a Motorola proto board for dataloging engine stat.

The original poster, like he said has no idea what he's doing.

A PC is a programmable microprocessor already, why would you add one to read sensors?

Fuel Curve, more like fuel map. Unless you've figured out a way to calculate amount of fuel needed fast enough at 8000rpm which mean it gotta be done in 0.0075 sec or faster.

Most car use return fuel system which run at constant pressure which the ECU got no control. Some new car use returnless system which ECU does control fuel pump speed.

MAP sensor output voltage, MAS sensor could be voltage or pulse.

Spark timing depends on pulse signal from crank or cam sensor which could be from distrubutor.

If you want to build one for your own car, have fun. You have a lot to learn. Buying one off the shelf is your best bet. By the time you add all the circuit board for sensor input and control output, it'll cost more then a aftermarket one.

If you want to build one for sell, good luck. A PC cost much more then a purpose build ECU without all the extra parts.

There are PC power supply that use 12V DC input.

Also heat management and size for the PC.

A better way is to use microprocessor and build everything around it to make a ECU. Motorola is a good source for microprocessors.

If you have no idea what I'm talking about, you should consider doing something else.

Pineapple

Register to Reply
Guru

Join Date: Aug 2006
Posts: 4542
Good Answers: 246
#19
In reply to #17

Re: Voltage Sensor to Computer Interface

03/21/2007 1:53 PM

If you want to build one for your own car, have fun. You have a lot to learn. Buying one off the shelf is your best bet. By the time you add all the circuit board for sensor input and control output, it'll cost more then a aftermarket one.

This is certainly true. I'd guess that all the I/O pieces might cost more than an entire aftermarket ECU. (In a way, when you buy an after market ECU, you are paying mainly for I/O -- the processor is almost incidental.)

As several have said, Phoenyx seems to be reinventing the wheel. A laptop is remarkably ill-suited to doing what he wants to do (other than as a programming interface). Most of the stuff surrounding the processor in a laptop is unnecessary for running an engine, and most of the stuff required for running an engine (and already in an ECU) is lacking in a laptop.

It's a little like building a laptop-based clock with an hour glass as the time base. Using a vision system, a laptop could be used to count grains of sand, and then show, in a digital display, how much time has elapsed. But why?

__________________
There is more to life than just eating mice.
Register to Reply
Guru

Join Date: Aug 2006
Posts: 4542
Good Answers: 246
#18

Re: Voltage Sensor to Computer Interface

03/21/2007 1:07 PM

Phoenyx:

Here's a link to the manual for the software used for programming the Electromotive TEC3 engine management system. It may give you some ideas for you own system.

http://www.directignition.com/pdf_files/WinTEC2SUG.pdf

For your project, it might be worthwhile to purchase a TEC3 or similar fully programmable ECU. In using it on your prototype vehicle, you will come to understand the nature of all the required inputs and outputs, and can get a feel for the state of the art in these devices.

Most of the fully-programmable after market ECU's are nearly flawless in terms of performance: in other words, you can make many modifications to a car's engine, but still (and pretty quickly) get the ECU to deliver precisely the right fuel quantity and spark timing for optimum performance at every engine rpm and load. Most enable you to do this tuning while doing dyno runs, using a laptop for the programming interface. While these after-market ECUs can provide better performance for even an otherwise stock engine (and are often a necessity for a modified engine), they don't provide better performance and lower emissions -- the manufacturers spend hundreds of hours in dyno testing to come up with an optimum mix.

Having done the programming of the ECU, then the last thing a racer wants in the car is the laptop -- the ECU is lighter, simpler, more reliable, and built for the purpose. I wonder if perhaps buying a unit like the TEC3 might satisfy your urge to learn about engine control.

__________________
There is more to life than just eating mice.
Register to Reply
Anonymous Poster
#21

Re: Voltage Sensor to Computer Interface

03/21/2007 4:33 PM

There is also Greddy E-Manage.


Pineapple

Register to Reply
Guru

Join Date: Sep 2006
Posts: 4545
Good Answers: 90
#22

Re: Voltage Sensor to Computer Interface

03/21/2007 9:52 PM

Building muscle cars ain't what it used to be. Imagine needing Linux to help eke out that last bit of horsepower from your fully-blown, nitro-injected '55 Chevy funny car. Dump the Linux and get some wheelie casters!

Register to Reply
Register to Reply 22 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.
Copy to Clipboard

Users who posted comments:

Anonymous Poster (4); aurizon (1); bhankiii (1); Bill (2); Blink (3); Cornstoves (1); GreenChoice (1); lshurtle (1); Neo13 (1); Phoenyx (2); Randall (1); Ron (1); Shawn33 (1); user-deleted-13 (1); y eye (1)

Previous in Forum: Amateur Radio Satellites   Next in Forum: Mobile Charger
You might be interested in: Computer-aided Design and Computer-aided Manufacturing Software (CAD/CAM), Interface Level Measurement Equipment