I just completed the bring-up on my DIY-WB board, and got to the last part where if it takes longer than 45 seconds I need to put the extra resistors in parallel with R4. The extra resistors in my kit (5 of them) are 10K 1% 1/8W. Those won't change the resistance more than about .1% per resistor added, is this correct? Or should the resistors be lower in value?

One web page I found says the voltage across R4 during warm-up should be about 1.25V, on mine it is over 1.3V.

Any help will be much appreciated.

Thanks,

John.

 

First thing ....

How are you powering the unit? If you are powering it via the cigarette lighter then verify the voltage at the WB box. I just went through this and was wondering why my WB was taking forever to heat up and wondering why it was giving me really funky readings. As it turned out ... I was only getting 12.5V from my cigarette lighter I had to run a separate power and ground specifically for the WB just to ensure it would get 14+ volts.

Also - my WB light will not come on until I actually start the car. Problem is - although I am now getting 14+ volts at idle, I am getting less until I actually start the car. But, as soon as I start the car the 'ready' light comes on almost immediately. My procedure is to key-on the ignition and allow the WB to have 30 seconds to heat up. Then I start the car and the light comes right on.

Anyhow - just verify your voltages before doing anything.

Thanks again to the person who helped me troubleshoot my unit recently! You know who you are! Woot!

Tim

 

Currently I am using a bench power supply, putting out about 13.5V, so I think that I am OK there. I looked at the DIY-WB mailing list archives and found out that I need 15 ohm resistors, presumably 1/4W. I will get some and start putting them in parallel till I get it down to a minute or so. Then I'll mount it in my car and give it a run.

One other thing, I am using three parallel wires in a 9 pin serial cable. I think the individual wires are bout 26 ga. I should measure the voltage drop in my wires and see if that might be the problem. Maybe I can find a 9 pin serial cable with beefie wires.

 

Don't judge the warm up time without being at the proper voltage ie in car.

A serial cable for the heater?. I doubt that will work out right.
While bulky and ugly, I use test probe lead wire.

Yes, 1-2 15 ohmers should be the max, IMO. To fast will shorten sensor life.

 

I put two 22 ohm resistors in parallel with R4, and now she warms up in about a minute.

Problem solved it looks like.

Looking at the circuit, it looks like as long as you have at least 12.75V at the input (at 25 degrees C) it should work fine. you will need another quarter volt or so at -55 degrees C