Hello, I am looking for someone that could help me build a timed PWM circuit to test fuel injectors. Basically I need a 12V circuit that when you push a button it would send a PWM 12V signal to pulse and open the injector you have it hooked to. This way with a fuel pressure gauge you can pulse each injector for the exact same amount of time and see how much pressure changed on the gauge to see if the injectors all are flowing about the same amount of fuel or if one's partially plugged so the pressure wouldnt drop as much as a good injector. I really dont know where to start. I would even pay someone to build just the circuit for me. Thanks. I do have soldering skills and can read a diagram, I just dont know how to time the system so it would pulse the exact same amount of time everytime a button was pushed. I was thinking a 555 timer but i dont know how to program one or how to incorporate it into a circuit. Any help would be great as my old one i bought got stolen and they are about 400.00 new. The one I had did 3 different settings but this homemade one doesnt have to be that fancy. Here is one similiar but I have a friend who has one and it's not really accurate. http://www.amazon.com/OTC-3398-Inje...OO/ref=sr_1_10?ie=UTF8&qid=1298971427&sr=8-10

 

$400 is a bit mutch. My tester is fixed pulse & i use time taken to inject a measured amount. Im sure someone here can desighn what you want. This gets used for checking Ign modules & coils.

 

Thats exactly what I am looking for. Are you interested in building one to sell? Thanks. Like I said, I really dont like the 140.00 one they have at amazon. Or could you atleast email me a complete component list and maybe a clear drawing schematic. you built exactly what I was looking for.

 

I will redraw the circuit using a more common driver transistor.

 

wow, Thank you VERY much. I sure would appreciate that. I will do the best I can. Sometimes with my head injury my thinking skills are not great so I may ask questions even after you send me an upldated Diagram. Thanks

 

Heres the circuit. parts are Q1, MJH10012. Q2,BC337. D1-2, 1N4004. ZD1-4, 75V Zenner diode 3Watt. LED. C1,10nf. C2,2.2uf. VR1, 10K. R1, 100 ohm 5Watt. R2,1K. R3, 560 ohm. R4, 2.2K. Interesting profile I used to work as a mechanic for a Ford dealer.

 

Hello kellogg49055,
I received your E-mail.
As my signature line states, I don't help people via E-mail, as it defeats the purpose of the forum.

However, your question is:

hello, I was wondering if you could tell me where I can get software

like you use to draw schematics? Thank you very much.

I've been using LTSpice, a free program from Linear Technology, for PSPICE simulations.
Their website is here: http://www.linear.com/
The LTSpice download page is here: http://www.linear.com/designtools/software/
You can register if you like, or not. They only send out E-mails occasionally about new product announcements, and I generally find them interesting.

You should register with the Yahoo! LTSpice Users' Group, which is here:
http://tech.groups.yahoo.com/group/LTspice/
There are lots of free models and symbols available for downloading, and a message board for getting help. You'll need to create a Yahoo! account, which is free.

LTSpice takes a bit of getting used to. Try running some of the examples, just to see what happens.

After simulation, if I'm going to make a circuit board, I'll re-draw the schematic in Cadsoft Eagle's schematic capture program, and then create the board from the schematic.
They have a freeware version available for download here: http://cadsoftusa.com/

Eagle is a rather complex program, but you can learn the basics by going through Sparkfun's Eagle tutorial:
http://www.sparkfun.com/tutorials/108

 

Heres the circuit. ...

Don't forget the fuse.

 

Hi Wayneh, oops! forgot fuse in diagram. The built unit does have a 10A in line fuse.

 

I cant seem to be able to find the MJH10012 transistor if you can send me in the right direction I sure would appreciate it. I did find one that was MJ10012 without the H but I dont know what the difference is...

 

Another equivelent to a MJH10012 is BU941P.