[sti robot]

...I maybe be doing oil temp as the next gauge. I have to learn about voltage gates first (change readings done in terms of resistance into ones in terms of volts). Senders are cheap btw: http://www.egauges.com/vdo_sgrp.asp?...erature_Sender The hard part would be to map the sender's output to an actual temp reading. The easiest way to do this would be to hook up a multimeter to a sender that is already connected to a gauge and take readings from both and figure it out from there.

[Mack]

I'd be down for that. I was looking at what DEFIs cost and I just can't justify it.

[4banger]

Originally Posted by sti robot

The hard part would be to map the sender's output to an actual temp reading. The easiest way to do this would be to hook up a multimeter to a sender that is already connected to a gauge and take readings from both and figure it out from there.

Any idea how linear the response between volts and temp is? If it is linear, it might be easier to do an experiment with a sender, a pot of water, your stove and a thermometer. The only bad thing is that the water will only get hot enough to boil. So if it isn't linear, this won't work because I don't think the range (32-212) will be useful. Otherwise, are you thinking of using someone who has a temp gauge already installed in their car?

[sti robot]

Originally Posted by 4banger

Any idea how linear the response between volts and temp is? If it is linear, it might be easier to do an experiment with a sender, a pot of water, your stove and a thermometer. The only bad thing is that the water will only get hot enough to boil. So if it isn't linear, this won't work because I don't think the range (32-212) will be useful. Otherwise, are you thinking of using someone who has a temp gauge already installed in their car?

Yes, I was thinking about using someone who has a gauge already installed in there car.

Temperature gauges can take several forms. From what I've gathered oil and water temp sensors are RTD's built into special housings (the bolt looking senders). These housings ground to the block/pan and usually have a single "hot" wire coming off of them.

Thermocouples ( http://en.wikipedia.org/wiki/Thermocouple) usually require the use of an amplifier due to their nature (special metal compounds that change their resistance in a predictable non-linear fashion based on temperature).

Thermistors ( http://en.wikipedia.org/wiki/Thermistor) are different in that they change resistance (not voltage) based on temperature. If the sender changes resistance then it is essentially a thermistor (or RTD). The interesting thing is that available industrial thermistors only seem to go up to 300 deg F. Thermocouples seem to be what people are using for higher temps. For instance, I am certain that EGT probes are thermocouples.

There are also RTD's (http://en.wikipedia.org/wiki/Resista...ture_detector). These are similar to Thermistors but go for higher ranges of temperature. Unfortunately they are more expensive (on the order of ~$15 where thermistors are ~$5).

So, thermistors it is...I guess.

[sti robot]

I believe this is one of the company that oem's the senders: http://www.ussensor.com/prod_rtds_prob_thr.html . I be some of these are the same exact items you'd get with an autometer, cyberdine, vdo, stewart warner, etc. gauge. The plus to finding this is that I can probably find someone who sells these and I have documentation to tell me how they are calibrated (delta ohm to delta temp) vs figuring it out on my own with a multimeter.

[4banger]

Originally Posted by sti robot

I believe this is one of the company that oem's the senders: http://www.ussensor.com/prod_rtds_prob_thr.html .

Great find, especially if they are in the $5 price range.

[sti robot]

After looking at the page they seem to be an oem. On the page is says to contact them to get some made to your specs. I'll shoot them an email when I get home from work and ask if a retailer sells them or if I could get a sample/pricing/etc.

Digikey sells their basic RTD sensors and that's how I found them. Those are ~$13 and would be great for IC piping temps, brake temps, etc. The threaded ones would be great. The have ones that are essentially gauge senders in the subaru thread size and they have small ones that you could use to tap into your cold air intake or IC piping.

[sti robot]

demo movie (all sensors are random number generators at the moment):

www.randomcrap.us/otherjustin/modes_demo.mov

...also i don't like how the numbers shift so i think i'm going to fix that next.

EDIT: I found a fix for the number shift/flicker...I should be able to implement it shortly.

[4banger]

Looks good!

How do you cycle through the various functions?

[Mack]

what about engine temp and g rating on one screen?