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Old 04-10-2008, 09:37 PM   #1
malloy1
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Default Need a circuit to produce a 12V square-wave output signal

I need a speed signal to feed pin 34 of an LH2.4 system. I'm planning on installing an '90 B230F engine from a 240 (I have a whole parts car-so I want to use the LH2.4 fuel/ignition system) into an '61 P210. So, no speed sensor in the rear axle like the 2.4/2.2 cars. I understand that the LH2.4 system requires a 0-12 VDC squarewave (50%/50% up/down) signal to pin 34 to run correctly.

I posted something on the "performance & suspension" section, and seems that the driveshaft flange bolts could be used as a trigger wheel, and an ABS sensor mounted on the transmission could produce the correct signal.

http://turbobricks.com/forums/showthread.php?t=131814

If anyone has a suggestion on how to build a circuit (either with a ABS sensor or any other sensor) to give the correct signal to pin 34, I would appreciate it.

Paul
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Old 04-11-2008, 02:38 AM   #2
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I will try to post something later tonight. A few NAND, capacitors, diodes and resistors should be able to do it. And you could put it directly in the ECU if you want.
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Old 04-11-2008, 08:17 AM   #3
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I'm not sure what kind of sensor the ABS sensor is, I assume it's a 2-wire hall effect or a VR? I'm glad somebody understands how to make it work.

I think an external circuit would be best, and have the output go into pin 34. No messing with the ECU, just a stand alone unit in case something goes wrong.

Thanks-

Paul

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Old 04-12-2008, 02:53 PM   #4
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I tried to make a simulator for you guys, but it didn't work for some reason. The output of the simulator was what I expected, but it didn't do anything for the ECU at all.

I wonder if the ECU knows that you are driving and estimates when to expect a signal? I have to look into this.
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Old 04-12-2008, 03:11 PM   #5
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Originally Posted by malloy1 View Post
I'm not sure what kind of sensor the ABS sensor is, I assume it's a 2-wire hall effect or a VR? I'm glad somebody understands how to make it work.

I think an external circuit would be best, and have the output go into pin 34. No messing with the ECU, just a stand alone unit in case something goes wrong.

Thanks-

Paul
if the abs sensor is a VR type, it is not a square wave signal, the ecu would have to "condition" it to make it so

have you tried to tap into the crank position sensor and use that signal??
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Old 04-12-2008, 06:58 PM   #6
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Originally Posted by frpe82 View Post
I tried to make a simulator for you guys, but it didn't work for some reason. The output of the simulator was what I expected, but it didn't do anything for the ECU at all.

I wonder if the ECU knows that you are driving and estimates when to expect a signal? I have to look into this.
Appreciate it! I can't find any information on how the speed signal is used in the LH2.4.

Paul
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Old 04-12-2008, 07:14 PM   #7
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if the abs sensor is a VR type, it is not a square wave signal, the ecu would have to "condition" it to make it so

have you tried to tap into the crank position sensor and use that signal??
I've looked for information on the ABS sensors, but can't find anything on what type of sensors Volvo used on their ABS systems. I only suggested the ABS sensors because they are built to be mounted by the tires (I'm thinking durability).

Any suggestion on a Hall sensor that could hold up being mounted under the car? What about the impulse sensor in the rear axle? That has to give out the right signal, but what about being durable under the car?

I suggested tapping the flywheel sensor, but when the car is stopped, the sensor would still give a pulse signal. Any idea on how the signal could be tapped and converted?

Paul
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Old 04-13-2008, 12:32 AM   #8
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dude, we need something like this:

Dynolab.com

just goes in series with the speedo cable. fuggin smooth.

ryan
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Old 04-13-2008, 12:44 AM   #9
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more goodness:

http://www.jagsthatrun.com/V8-chapte...ed-Sensors.pdf

ryan
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Old 04-13-2008, 12:47 AM   #10
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y mas:

http://www.waltech.org/21stcenturyho...sinstall.shtml

ryan
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Old 04-13-2008, 02:28 AM   #11
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Appreciate it! I can't find any information on how the speed signal is used in the LH2.4.

Paul
The speed signal is used to know when to cut fuel on engine braking, when to raise the idle based on road speed, if it needs to enrich the mixture at quick throttle response, if it needs to enrich the mixture due to high speed for long periods of time, plus a lot of other things it has to expect in changes to the engine speed based on driving style.

If that function was abscent in the ECU, it would not have made a very big difference and most people would probably not miss it. But it does make a difference in driveability.
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Old 04-13-2008, 08:27 PM   #12
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any chance of fudging an abs-style tone ring into one of the front disk hubs to make the signal?

that way the signal is actually valid for LH instead of trying to trick it.
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Old 04-13-2008, 08:32 PM   #13
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any chance of fudging an abs-style tone ring into one of the front disk hubs to make the signal?

that way the signal is actually valid for LH instead of trying to trick it.
What happens if you get wheelspin at the rear? Does LH2.4 think the propshaft has snapped

As folk are looking at this can anyone tell me the number of triggering 'teeth' there are on a 940 diff?

It would not take me long to do it myself but it is one more of those five minute jobs I never get five minutes for.

Rob
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Old 04-13-2008, 08:41 PM   #14
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What happens if you get wheelspin at the rear? Does LH2.4 think the propshaft has snapped

As folk are looking at this can anyone tell me the number of triggering 'teeth' there are on a 940 diff?

It would not take me long to do it myself but it is one more of those five minute jobs I never get five minutes for.

Rob
im sure its not listening to the signal all that much durring wheelspin. the signal seems soley drivability related, not power related.

i know, my 940 throws the axle sensor code occassionally. and i can tell when its going to before it does.
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Old 04-14-2008, 10:48 AM   #15
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Ryan-

Those links look very promising! One of them had a trigger wheel mounted to the driveshaft, which is what I was thinking (just on the front section):



I like the ones that mount on the speedometer cables, but I would think it would be better to mount it next to the speedometer not on the transmission.

Still need to figure out if the output to any of these can produce the right signal or if it needs a circuit to feed the ECU. Also, need to figure how many pulses the ECU needs per mile.

Paul
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Old 04-14-2008, 11:10 AM   #16
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Quote:
Originally Posted by frpe82 View Post
The speed signal is used to know when to cut fuel on engine braking, when to raise the idle based on road speed, if it needs to enrich the mixture at quick throttle response, if it needs to enrich the mixture due to high speed for long periods of time, plus a lot of other things it has to expect in changes to the engine speed based on driving style.

If that function was abscent in the ECU, it would not have made a very big difference and most people would probably not miss it. But it does make a difference in driveability.
That makes sense! From what I hear, a LH2.4 car without the speed sensor input will not idle correctly, but it has more dramatic implications than I thought.

Paul
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Old 04-14-2008, 11:15 AM   #17
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Originally Posted by frpe82 View Post
I tried to make a simulator for you guys, but it didn't work for some reason. The output of the simulator was what I expected, but it didn't do anything for the ECU at all.
Did you ever figure this out? I'm sure we'll need a circuit for any sensor we use? I would be happy to pay you for your time. If you need anything, let me know.

Paul
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Old 04-15-2008, 05:53 PM   #18
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Did you ever figure this out? I'm sure we'll need a circuit for any sensor we use? I would be happy to pay you for your time. If you need anything, let me know.

Paul
Well... it seems as though the ECU anticipates that the car should be moving according to load and rpm, and when fed a constant pulsetrain from a simulator circuit it sees this as something that is not accurate. That is why it never works. It has to change based on rpm.

But I don't think you need to make a circuit if you just mount a sensor and a wheel somewhere in the driveline.
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Old 04-15-2008, 07:37 PM   #19
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Thanks again!

I thought the speedometer sent the signal to Pin 34 of the ECU, so I can just bypass the speedometer, and send the signal directly to pin 34. Do I just apply 12V to one wire of the speed sensor, and the other would be the signal wire to Pin34?

Paul

Last edited by malloy1; 04-15-2008 at 08:16 PM..
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Old 04-29-2008, 08:20 AM   #20
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Thanks again!

I thought the speedometer sent the signal to Pin 34 of the ECU, so I can just bypass the speedometer, and send the signal directly to pin 34. Do I just apply 12V to one wire of the speed sensor, and the other would be the signal wire to Pin34?

Paul
What if You take sensor from 240 rear-axle, make impulse wheel with 4 teeth. All these mounted at gearbox output shaft. Then take speedo electronics from the same car as sensor. Connect according 240 manual. This is the way to get signal-levels, dutycycle etc. things right on. I mean, i have done more than my share of building measurement systems and sometimes these digital signals are PITA. (Its PNP NPN transistor thing)

Or just "swap" rear-axle from 240 ?
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Old 04-29-2008, 09:18 AM   #21
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Thanks again!

I thought the speedometer sent the signal to Pin 34 of the ECU, so I can just bypass the speedometer, and send the signal directly to pin 34. Do I just apply 12V to one wire of the speed sensor, and the other would be the signal wire to Pin34?

Paul
The speedometer contains a circut which converts the sine-wave from the diff sensor into a square wave for the ecu's. The output is an open transistor emittor, and pulls the ecu-input low. It can not be replaced with just a cable from an ABS sensor. When installing a 960 driveline in a 242, I removed the circut board form the speedometer (not to be confused with the instrument cluster), and used this to get signals for the ecu's and 240 speedometer
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Old 04-29-2008, 10:15 PM   #22
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The speedometer contains a circut which converts the sine-wave from the diff sensor into a square wave for the ecu's. The output is an open transistor emittor, and pulls the ecu-input low. It can not be replaced with just a cable from an ABS sensor. When installing a 960 driveline in a 242, I removed the circut board form the speedometer (not to be confused with the instrument cluster), and used this to get signals for the ecu's and 240 speedometer
I thought about ripping a speedometer apart to see how things work. Can you describe in some more detail on how you did? Did you use the speed sensor from the rear axle? What part of the speedometer box did you use? Did you just use the electronic speedometer circuit board?

Thanks-

Paul
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Old 04-30-2008, 03:34 AM   #23
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I thought about ripping a speedometer apart to see how things work. Can you describe in some more detail on how you did? Did you use the speed sensor from the rear axle? What part of the speedometer box did you use? Did you just use the electronic speedometer circuit board?

Thanks-

Paul
I fitted a '92 240 rear axle (was going so ditch the old one anyway) with a 48teeth tone wheel and stock speed sensor. The idea of a tone wheel on the driveshaft sounds somewhat tempting, but you need to take the differential ratio into account, substituting a 48 diff tonewheel with a 13-14 teeth driveshaft tonewheel (48/3.31, 3.54, 3.73) With this small number of teeth, it is allmost impossible to separate the different diff ratios, but I don't know if this is critical to the ECU. I would think it is possible to adapt a tone ring and sensor setup to your diffif it is...

I ripped the electronic speedometer circut board from a 960 speedometer. I removed the connections to the electronic motors running the needle and odometer. I was then left with the bare circut board which I fitted in a case from an old mercedes ICU, which I had stripped of its old circut board. Then it is only about hooking up +12V, ground, sensor + and -, and the output to the ecu (I was running both the ecu, and speedometer of the same output, and had to make a separate circutboard with a couple of transistors and resistors to split the signal, but this shouldn't be a problem to you.) The ECU expects a 12 pulse/rev signal, and this is converted from the 48 pulse signal from the diff by the speedometer circut board (the 48 pulses on later volvos are to give the TCU and ABS system better resolution, and is provided by a separate speedometer output. Older speedometers run of a 12 pulse tone ring. You need to make shure that you get the correct speedometer circut board for the tone wheel you plan on using.
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Old 04-30-2008, 10:41 AM   #24
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Try this Allegro part

http://www.allegromicro.com/en/Produ..._Numbers/0665/

It is a hall sensor with built in magnet. No other circuitry required. Ask for a sample.
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Old 04-30-2008, 01:19 PM   #25
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Try this Allegro part

http://www.allegromicro.com/en/Produ..._Numbers/0665/

It is a hall sensor with built in magnet. No other circuitry required. Ask for a sample.


Digi-key is a supplier of it. $5 each. The picture looks like it's not really durable enough to be mounted out in the elements.

I did find this Hall sensor made for the automotive market. I really didn't want to post anything until I tried it out. I have an order in, but it's on back order for the next two weeks.



http://www.bbautomacao.com/proddetai...rod=CYGTS101DC

Spec sheet is here:

http://www.bbautomacao.com/home_hall...YGTS101DC.html

It needs a pull-up resistor circuit, but thats easy enough.

If this doesn't work, I'm going to try and pull the circuit board from the speedometer.

Paul

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