[JRoque]

Hi Joe. Quite the application you're setting up to do.

I didn't see a low limit in the datasheet but their performance charts start at 6 volts which seems to imply you'll get the best performance starting at that voltage. However, looking at the block diagram for the part and with the exception of the zener, all other parts are likely to work at 5V.

You can also consider a buck/boost regulator that would let you select your working voltage and input something that's lower or nigher than that... or varies as is the case with vehicles. I like Linear Tech (linear.com) parts but others like National, Maxim, TI, On Semi, etc have these parts available.

After you're done with the analog version of your project, look into microcontrollers and how they can help. A micro would allow you so much flexibility that it's hard to pass on. For example, you can write a subroutine in your micro that loads a "towing" profile when you plug the brake lights from the trailer. That would make the OD, etc behave exactly how you want it during towing. You can also add cool things like LCD or LED displays that show the current conditions/profile, etc or even preset buttons to load these different profiles. Hmm dial up your HP.. that sounds nice.

With a micro, you would skip the LM2907. The pulse can be conditioned a bit and fed into an interrupt on the micro that'd be it. Not sure how you get your temperature reading but many micros have analog to digital converters that can do that directly from a temp sensor.

Micros have a steeper learning curve, I guess, but the flexibility beyond that is great.

Regards,
JR

[Al_The_Man]

Micros have a steeper learning curve, I guess, but the flexibility beyond that is great.

Regards,
JR

And with 40yrs as a programmer, should be a piece of cake

These tutorials helped me when I got into Pic's, some thing to bookmark if you do go that route. http://www.winpicprog.co.uk/pic_tutorial.htm
Al.

[oegeorg]

Thanks JR and Al,

I really hadn't known before today about the availability of microcontrollers at the prices I have been looking at just surfing around today. I think I would have more trouble finding out what they can do than in progamming them. I'm pretty good with C since I have written a lot of programs for main frame type computers and some stuff for PCs. And, lo and behold, there is a free ANCII C compiler for microcontrollers. Very interesting to say the least.

I get my temperature reading for EGT from a K type thermocouple. The voltages from that thing range from about 3 milivolts at 200 degrees to almost 40 milivolts at 1800 degrees. Not a linear pregression either.

I can control the truck transmission to some extent with electronics, but most of it is controlled by a fly weight governor. No electronic messing with the engine either. The '94thru early '98 Cummins powered Dodge trucks are probably the last of the mechanical engine and drive trains made in this country. Not a computer skooter at all. In late '98 the fuel system switched to computer control so they can be "chipped". The earlier trucks like mine are using cutting edge technology from WWII. The only way the thing will throw a CEL is if the alternator dies. I understand that kind of diesel engine so I'm having a lot of fun with mine.

Most of the perpose of these small projects I'm doing on the truck are to get up to speed (sort of) on modern electronics. This particular one is because it seems kind of silly to be operating my automatic transmission manually with switches like I'm doing now.

I'm thinking very strongly about getting this project to work and then seeing what I can do with microcontrollers.

Thanks guys,
Joe

[lerman]

I strongly recommend AVR micros. See http://www.avrfreaks.com for tools and so on. WinAVR is a complete development environment on windoze for the AVR family. Or use the same tools on Linux. In either case, the tools are the same.

Ken

[pastera]

Use an AD597 to interface the thermocouple - datasheet gives a reference circuit.
LM2940 for the regulator - it's an automotive part, it's cheap and simple to use

Get a micro with plenty of I/O and use optocouplers to hook up to every input you think you could possibly use (brake switch, neutral safety switch, etc...).

Aaron

[oegeorg]

Thanks for the reply. I'm using an LM393 voltage comparator and four resistors to detect the two thermocouple threshold points I'm interested in. That is simple and works well. I will investigate the micros and do some studying about how to use them. I have a bunch of bright(?) ideas rattling around in my head for those things.

[T.L.A.R. eng]

You mentioned The torque convertor lockup staying on at low vehicle speed. If you add a n.o. pressure switch to the second or third gear oil circuit in the valve body, then run the switch in series with the t.c.c. solenoid, the t.c.c. will unlock as soon as you loose second or third gear. You would have to study the hydralic circuits to see where to tap into. You may have to use both worlds of electronic controler and hydralic switches to interface with the transmission to get the results you want. Just a suggestion.

[oegeorg]

Our friends(?) at Dodge have headed that idea off at the pass which is one reason I'm developing this circuit. The trans will NOT down shift if the TCC is locked. My VB has been modified to hold a lockup in 2nd, but there is no way to cause the trans to shift from 3rd to 2nd automatically with the TCC locked. I can make it shift from OD to 3rd by dropping the ground on the OD solenoid. The three gears in the main part of the transmission are all hydraulically controlled. I can deal with OD and TCC lockup because solenoids are used for that. 2nd gear is detectable because there is a test port for the front band which is only applied in 2nd. I really don't want to make any hydraulic mods to it because I would like to be able to give the circuit to some friends with the same truck. Thank you for the suggestion.

BTW. I managed to get the LM2907 RPM sensing to work. It would not work directly off the sensor, but it worked fine on the signal from the PCM to the tachometer.

[crack]

garrett have a nice little setup for measuring shaft speed.

http://www.turbobygarrett.com/turbob...ed_sensor.html

[crack]

sorry. double post.

[crack]

dammit. triple post. sorry

[cnczoner]

Just saw this thread, and not sure where it stands now, as I see discussions of thermocouples etc now. Did you ever solve this 120k rpm tach issue?

[bsharp]

I know this thread is old but after just skimming through some of it all I can say is Wow!
I was also looking for something simple that I could build and I found this.
http://www.josepino.com/circuits/ind...er-circuit.jpc
it is simple and to the point.
You could probably find all the parts by tearing stuff apart around the house "an old VCR, UPS, Older TV Remote".
Although I am not looking at reading 120k pulses!
I am sure that with a little playing around you could make this work.
"I just wouldn't trust an inductor "mag pickup" at 120K" dunno why? just wouldn't!
Probably old memory's kicking in from playing around with small engines with magneto ignition"
Personally I would use an opto sensor for something running 120k rpm.
http://search.digikey.com/scripts/Dk...?name=OR524-ND
you could probably scrounge one from an old computer mouse? As for the optical trip? I would use a metal disk and punch a hole in it then fix the slug from the hole back onto the disk above or below the hole. "should stay fairly balanced that way".
As this problem is a few years old you most likely found another solution.
I am just posting this as I to was looking for "Something Simple".
I was looking for something to read an encoder count on a spindle mounted encoder and convert it to a 4 to 20 ma current range. This will be the feed back on a VFD for a PID loop. Although what I plan on doing is totally different you are still basically doing the same thing. Taking a pulse and converting it to a linear.

[epineh]

Check your VFD, the ones we use at work (WEG) will accept an encoder pulse directly and you can set up a PID loop via the VFD.

There are a few IC's that are dedicated transmitters as well, eg :

http://www.futurlec.com.au/AnalogDevices/AD694JN.jsp

Good luck.

Russell.

[Al_The_Man]

I was also looking for something simple that I could build and I found this.
.josepino.com/

"I just wouldn't trust an inductor "mag pickup" at 120K" dunno why? just wouldn't!
Probably old memory's kicking in from playing around with small engines with magneto ignition"

The josepino link is virtually what the LM2907 does, mentioned in the first page posts, and do it for a couple of $.
The Auto motive sensors used in current automobiles like the Honeywell GT1 series, are good to 100khz, the sensed rpm will depend on the amount of sensor teeth.
Al.

[bsharp]

The josepino link is virtually what the LM2907 does, mentioned in the first page posts, and do it for a couple of $.
The Auto motive sensors used in current automobiles like the Honeywell GT1 series, are good to 100khz, the sensed rpm will depend on the amount of sensor teeth.
Al.

I agree with you on the LM2907 AL. And if I had one of those yesterday that is what I would have used. I was looking for something I could build from spare parts just to get going on things. On my spindle it originally used an inductive prox sensor. But I have an old encoder laying around and figured I could make use of the index and one of the a/b channels.

[bsharp]

Check your VFD, the ones we use at work (WEG) will accept an encoder pulse directly and you can set up a PID loop via the VFD.

There are a few IC's that are dedicated transmitters as well, eg :

http://www.futurlec.com.au/AnalogDevices/AD694JN.jsp

Good luck.

Russell.

Thanks Russell

I have a 2HP Hitachi L200 VFD. As far as I can tell it only has two analog inputs. One for current and one for voltage. I have the voltage input setup to be the Target Frequency "PWM from Mach3 to analog voltage". The L200 does have a built in PID differential equation. I was thinking I could use one channel of an encoder "a/b" to tightly close the PID using the current analog input. Then I could use the single Index from the Encoder as reference for Mach3 to do IPR interpolation.
Thank you for the info on the AD694JN it is exactly what I need.