Datalogging EGTs: Interest for a group buy?
 

I've been talking with Dan from DynoTune.org about his digital EGT gauges and what it would take to convert them to a 0-5v output. Seems like it's a fairly simple mod for him to make as his sender is already provides a 0-10v linear output to his digital gauge (0v = 0*c and 10v=1000*c).

Since he's got to alter these from his normal production runs, it'd be easier to offer these to the masses in the form of a group buy. I need to judge interest in this so that I can get him a working guesstimate of how many he might need to do.

The buy would be for
- Fast Response EGT probe w/ BNC connector and braided stainless cabling
- Sending Unit modified to linear 0-5v output
- Hopefully a bung to allow you to run the EGT probe in your stock O2 sensor hole.

I'm looking to source the bung/adapter now. I think the Autometer kit comes with one so someone's got to make 'em. If anyone knows of a source I'd appreciate it. He's also noted that the probe has held up very well in rotary applications.

So far we're talking about a kit with no gauge. I don't know what it would take for him to be able to modify his gauge to read the 1/2 signal but I'd assume it could always be added on at a later date, but log-ability is what we're after here.

I'm also waiting for a price from him. I'm assuming it'd be in the neighborhood of $200-$250.

Who's interested? He's burning the midnight oil getting another few products ready right now so it'll probably take a few weeks to get a good answer from him.

I am interested. I was just thinking of how to do that the other day.

If all you need is an voltage reducer to make 0-10 Volts into 0-5 volts you can do it for less than $4. All you need is (2) 33K resistors, a .1uf capacitor, a small piece of electronic perfboard, wire and solder. It is a very simple circuit. Anyone interested can contact me.

Yeah, I know all it takes is a simple voltage divider circuit on the back of this, but there are many that want something complete and packaged without wires hanging out of stuff.

If you are interested in a complete Ghetto Mod solution (egt sensor, amplifier, cold junction compensation, linearizer, and voltage reducer for under $100 I would be glad to share the schematics. For another $100 you could have a digital backlit display.

I'm absolutely interested.

I didn't realize that unit was 0-10v and had a seperate sender until after I began talking to him. The only other solution I really knew about was the Defi-gauge mod from the big list, and I didn't really want a gauge, nor know how well it worked.

Are you using one of these Ghetto-EGT's?

Schematics
 

Here is the schematic for the main TC amp. I will followup with the voltage divider in a few minutes

Voltage divider
 

OK Here's the divider

BTW, I have used this setup with rotary and non-rotary applications. Because the AD595 IC is "instrument quality", this "Ghetto Mod" is EXTREMELY accurate and may outperform most commerical units for datalogging applications.

Jebus, there isn't anything to that circuit. Sold me on it.

I was just on analog.com and couldn't find anything referencing AD-495. Maybe I'm just not seeing it. Someone else carry them for retail by chance?

Thanks much for the help, Jeff.

My screwup... its AD 595 not 495. I do that constantly and should know better by now. The circuits are unchanged I just labelled it wrong.


Try here

http://www.analog.com/Analog_Root/pr...,AD595,00.html

Corrected Schematic
 

Here is the schematic with the correct designation for the AD595.

Thanks.. got a few samples on their way.

Curious if you know of some good, free circuit design software or perhaps some easy way I could take a laser printed design right to pcb without dicking around with little sticky pads & sharpies?

I appreciate the info.

DigiKey also carries the AD595 in the AQ and CQ type
AD595AQ-ND: $10.43 each (not in stock)
AD595CQ-ND: $16.98 each (in stock)

BTW total actual costs for the TC amp circuit is between $35 and $40 and that includes a $5 Serpac case.

Total actual cost for the reducer is about $9.00 including case.

Build time on the amp circuit is between 30 and 60 minutes for an obsessive/compulsive and includes bench tests.

Build time on the divider is about 10 minutes

As for pcb software try ECAD Pro.

Since I originally drew the circuit, I forgot that I added a resistor for better supression of possible voltage spikes. Here is the updated and hopefully final schematic. It is not a big deal but it should help.

Now it looks just like the one on AutoSpeed's site. I keep meaning to join up with them.. there's great DIY home brew stuff in there.

Great minds think alike. Autospeed is where I got the idea to add the resistor and the info on how to output to the led backlit display.

Thanks for all the input Jeff. I will be using your divider on my new fuel pressure guage.

Anyone interested in adding alarms etc to the TC circuitry should dowload the following data sheet for the AD595

http://www.analog.com/UploadedFiles/...7AD594_5_c.pdf

Interesting project. How is it working out guys?

I bought a Defi d gauge EGT a while back and opened it up. I was able to tap into a lead of a chip inside it add a resistor and send a wire right out of it for a 0-5v output. total cost to me 0.40$ + the gauge. if anyone is intrested in exactly how I did this (i have been logging it for a while) I was able to do the same for fuel pressure on the defi gauges as well. I can give you a write up of the procedure if you PM me.


Also it looks to me like this chip would work well in an AIT type setup. that way I could measure the a intake temperature change across the intercooler.
Of course modifying the stock sensor with the faster delphi unit and placing it on the cold side of the intercooler would do that pretty well too.

AHH I know Ill make this circuit and measure/log Oil temperature

Jeff,

Nice work on the circuit, thanks, I intend to do two. Will the output from the amplifier overcome a pullup of 1k Ohms to 4.7K Ohms? Pullup was the language of the Motec tech guy for the inputs. It will be nice to have constant logs for each rotors EGT with Lambda and all the other engine sensors to tune with.

Kevin T. Wyum

Ever find that bung? I have a greddy egt just sitting in the garage waiting for me to get the exhaust tapped. Since I have disconnected my O2 that would be perfect for me to use.


Thanks,

Does anyone still have these schematics anywhere? I'd like to see this. Thanks.

i run a double (front and rear rotor) circuit designed by jeff. it is dead on and w the Teamrip.com thermocouples is instantaneous. i have 6500 miles logged and would be unable to properly tune without it. the double circuit cost approx $30 plus the thermocouples which are $45 per... do not buy cheap thermocouples BTW.

i believe i do have the image of the circuit saved and will try to post it thursday.

jeff's egt setup feeds right into the auxiliaries on my datalogit and has been a huge help in tuning.

i literally gave away my two greddy analog gauges after comparing their readings w the digital setup.

check back tomorrow.

howard coleman