Help

I have currently built the two transistor circuit about 5 times. The third try worked briefly but was too noisy to get any data. Then it stopped working. Now when I try to use Craig's software I get an echo back of the stuff I sent but no response from the computer(730.) I have tried two different computers(730) and I have checked for continuity between the aldl connector and the computer. The computer(730) has a high(5V) signal any time the car is on and this never seems to change. Any thoughts on the things I might do next.

Thanks for any help

John

 

Do you have an ohmmeter/multimeter to test every point of the circuit when you're done? It's not the hardest thing in the world to solder together, if you are somewhat experienced, but I don't know you so I can't vouch for your skill level...

I have to admit, I found all the parts in the basement and put my cable together, only to realize (when it didn't work) that I was numbering the RS232 backwards, so I had to redo that.

 

Joel

Thanks for replying.

I got the circuit to work repeatedly. I removed the diode and reduced the resistor on the base of the transistor that pulls the data line low from 10k to 8k. Craigs software now connects everytime. Unfortunately I have encountered another strange problem. The software logs just fine if I am going steady down the road. It works better if I am decelerating. It doesnt work at all if I accelerate. I have checked all the connections and they seem to be very tight. Is it possible that engine noise could be blocking the signal on acceleration?

John

 

I don't see how engine noise could be causing the problem... sounds like something electrical maybe??

I'm no expert... when you accelerate, you see a slight increase in output from the alternator, up to a point. I dunno, hope you find the answer, tho!