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bertus
Moderator
Hello,
Are you able to build a generator yourself as in the schematic of post # 23:
https://www.electronicspoint.com/fo...se-generation-help.292079/page-2#post-1792001
It is much simpler and the duty cycle will always around 50 %.
Bertus
Are you able to build a generator yourself as in the schematic of post # 23:
https://www.electronicspoint.com/fo...se-generation-help.292079/page-2#post-1792001
It is much simpler and the duty cycle will always around 50 %.
Bertus
It seems a bit complicated
do you think something with the wave generator? Wave generator seems to be working because it does flash the led on slower pulses
Well, you've about done everything that I would have suggested! Have you put your 12volt LED from pin 20 to ground and see if that is flashing - you may have to turn the frequency down low on the lowest range. You don't need to go any higher in frequency than 85Hz as we calculated earlier (The end result is the frequencies are doubled, 100mph = 84Hz, 10mph = 8.4Hz - apologies to all.) so you can see the 1Hz flashing on the generator board and your LED. It may be the LED on the board that's getting hot or it's dropping resistor - or it could be the NE555 itself - digital circuits dissipate most of their heat when going from low to high voltage and back so the higher you turn the frequency the hotter it will get.
One question that has not been asked - was the instrument cluster working when you took it out of the vehicle? .......
One question that has not been asked - was the instrument cluster working when you took it out of the vehicle? .......
You mean without using the wave generator at all? Just the LED + to pin 20 and LED - on ground? I tried that and LED stays on.
One question that has not been asked - was the instrument cluster working when you took it out of the vehicle? .......
Yes the cluster was working perfectly fine. The speed is digital
I just tried that, and the led is flashing slowly on the lowest range but still no sign of the speed going up on the cluster, just shows 0mph.
The lowest speed is 1Hz which I suspect is too low to indicate but that's alright - we've shown that the pulses are pulling down pin 20. I suspect that the lowest indication on the speed will be 10mph or something like that so you want to adjust the frequency control so that you will have about 10 pulses per second which will be almost a blur - just turn it up gently and see if the speedo indication comes up. Don't go mad on it, remember only 85 pulses per second or so is 100mph! If there is still no indication, try removing your LED - I'm wondering if that is drawing sufficient current to pull down pin 20 all the time so that it's permanently low enough to stop the pulses being seen by the cluster input. Apart from that - I'm running out of ideas! I wonder if there's some connection that hasn't been made......have you got a full connection diagram for the cluster?
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I'm beginning to think that you need more than one 12v supply - especially as it says in the test diagram you sent " remove the assembly....with the connectors still connected". So you need to supply volts to all those pins - it may well be that not having something connected will inhibit something else working - the whole thing is far more complex than I earlier imagined. Where is the ground - I suspect it's pin 31. Do you have the car it came from so you can plug it in and just remove the plug from the wheel speed sensor and attach your pulse generator?
Below is a pic of the full pinout. The main connector is called K3. There is also a K4 connector but K4 connector is only for the turn signal wires.
The main +12v i've connected to pin 22. From the same power supply +12v connection I took a wire to a rocker switch going to pin 21 to mimic turning ignition on and off. Ground is 31 and 40 which i've merged together to the same ground. Pin 4, 25 and 26 are related to trip/odo reading which i've got working by connecting to the original switch. Pins 2 and 3 I got working via resistors against the ground too. I can't see any other inputs anywhere. From the full schematics, it seems like there is some sort of link between ignition (pin 21) and pin 20
I dont have the car it came from unfortunately.
The main +12v i've connected to pin 22. From the same power supply +12v connection I took a wire to a rocker switch going to pin 21 to mimic turning ignition on and off. Ground is 31 and 40 which i've merged together to the same ground. Pin 4, 25 and 26 are related to trip/odo reading which i've got working by connecting to the original switch. Pins 2 and 3 I got working via resistors against the ground too. I can't see any other inputs anywhere. From the full schematics, it seems like there is some sort of link between ignition (pin 21) and pin 20
I dont have the car it came from unfortunately.
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Here's something I don't understand. Nowhere in either test method you've sent to me does it say "observe the speedo" - all it says is "connect a 'scope to pin 20" and observe the waveform. Now in the schematic diagram pin 20 goes to a bit if circuitry and an output to pin 19 - NOWHERE does it go to any other part of the panel. The line across the top the other side of the diode just supplies 12v to the other bits and a voltage regulator. Have you ever seen this panel functioning on a test bench with a simulated wheel rotation? I'm beginning to think we've been chasing a herring of a red colour! Perhaps pin 19 feeds another bit of circuitry that converts the wheel pulses to road speed because there's nothing on any of those connections that looks vaguely like speedo!
I've heard of it being done but not sure if it was through simulated wheel rotation. I just thought seeing as it has speed input and output and the description from the technical notes posted previously for diagosing speedo issues seemed to look like that's how it works. I'm now thinking could it be the digital speedo information comes from the CANBUS but then what will the speed input and out signal be for?
Like I said before, all that bit of circuitry between pin 20 to pin 19 is just a bit of signal conditioning - it'll shape up the pulses and get rid of any interference - maybe the Mk1 version didn't have that and the signal went straight to those modules but they found that wasn't working well so they needed to fit an amplifier somewhere and the instrument cluster was the easiest place to put it. Pin 19 goes out to the engine control module which should be getting other inputs from the gearbox control module, throttle position, both engine and air temperature, air density and humidity - what the CANBUS is I don't know but its logical that one bus goes around the car with all this information on it. It could easily be carrying road speed information - it would be far more efficient than having multiple wires to each unit. What make and model is it, might try and find the schematic diagram - my Subaru is 'drive by wire' - just one coaxial cable goes round all the units - including the radio!
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