TIP120 for PWM idle valve wiring question

jasonsp6 · Post by **jasonsp6** » Mon Oct 31, 2005 6:55 pm

Hi guys,

I have a quick question... Hopefully I chose the right sub-forum.

I have a V3.0 PCB that I am in the process of assembling and need to support a PWM idle valve. I understand how to do the modification and use a TIP120 (and 3 short lengths of wire) in replacement of Q20, but wanted to know how much current the small traces on the v3.0 PCB are really designed to handle.

Also, what wire gauge are you guys using for the 3 short leads to connect the TIP120 to the Q20 holes?

Thanks for your assistance!

Matt Dupuis · Post by **Matt Dupuis** » Tue Nov 01, 2005 7:20 am

Dunno about the "designed to handle" part, but the traces on my old V1 board only started having trouble passing 15+ amps thru my injectors. I'm also not sure if they injector traces are the same thickness and width as all the other traces, but I do know the V3 board's traces were beefed up from the V1/V2 boards, so I'd say your traces will have no trouble surpassing the current rating of a TIP122.

I used 18 or 20 gauge wire - I forget which at the moment.

SRoss · Post by **SRoss** » Tue Nov 01, 2005 9:55 am

Wow, good thing I saw the title of this post. When did step #62 in the build instructions change? There should have been a sticky or something. I have been having problems with my PWM idle for a while now, I'll update it with the TIP120 and try it out this weekend.

i8dirt · Post by **i8dirt** » Tue Nov 01, 2005 7:04 pm

I suspect there should be no problem with the traces. I do not have a board in front of me to make sure but, the original circuit was designed for at least .8 amp (the rating of the transistor)... The typical fod pwm idle air runs at around 1.2 amps (100% duty cycle). Bout 50% more, sounds like alot, but unless the trace is like the width of a hair there should be no probs.

Mark