Trying to build an o2 sensor simulator but car forums are a bad place to ask . . . - Page 3 - diyAudio
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Old 10th July 2013, 12:22 AM   #21
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I was curious about the LED's drop voltage or other specs affecting oscillation rate. Everything seems to be in order, but the circuit doesn't work as it should.
I don't see how the LED's would affect oscillation rate.
I'm unsure about the LED's, but the circuit is this:
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Old 10th July 2013, 03:47 AM   #22
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Hi,
The components values are mussing in your drawing. We need the values you are using in your board.
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Old 10th July 2013, 04:00 AM   #23
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Oh yeah Here it is:
1x NE555 timer IC (or similar 555 timer)
R1 - 100k Ohm resistor (1/4 watt or 1/2 watt)
R2 - 1M Ohm resistor (1/4 watt or 1/2 watt)
R3 - 100k Ohm resistor (1/4 watt or 1/2 watt)
R4 - 10k Ohm resistor (1/4 watt or 1/2 watt)
C1 - 4.7 uF capacitor (rated to at least 15V)
C2 - 22 uF capacitor (rated to at least 15V)
D1 - 1.7V @ 20mA LED
D2 - 1.7V @ 20mA LED
(IMPORTANT: Please make SURE that the LEDs you use are rated to drop 1.7V. If they dont burn 1.7V, then your ECU will have to burn it for them, and that could cause serious damage. They are not simply for appearance!
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Old 10th July 2013, 04:57 AM   #24
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Hi,
First they recommended if you do not use pin 4 to connect it to pin 8. For a test remove R4 and if you can change the 1meg resistor for a 100K resistor.
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Old 10th July 2013, 10:44 PM   #25
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My LED's flat part is on the other small or "positive" terminal, but the flat part is the negative terminal.

If I'm reading my multimeter correct in the 2 mA setting I get "0.116" max (mA?)
I hope it's not an amp reading because that would be 116 mA of course?!
What should it be?

Also when the circuit is not connected to the o2 signal wire I get .0 to .9 volts, when the car is running. When I connect the signal out to the o2 sensor input of the ECU, I get .22 to .77 volts with the car running. Seems like my wire needs a ground, no? Will it still work?

Are my LED's the wrong mA rating?
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Old 11th July 2013, 02:07 AM   #26
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Hi,
The led flat goes to ground. Really what the LED's does it is simulating the O2 sensor voltage. The voltage across the diodes are about .8 volts. If your board it is connected to the car battery you just need to connect the two cables from the LED's and the ground wire. Make sure the voltage output it is less than .8 volts. If the voltage it is below .5 the car it is running rich and it is reading higher than .7 volt the car it is running leading. For a normal reading the voltage should be around .6 volts. The MCU it is looking for a voltage not a current. For a MCU voltage reading the voltage should oscillate between .2 volt to .8 volt.
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Old 13th July 2013, 03:20 PM   #27
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Did I wire this right?
So far it doesn't work.
The circuit oscillated from .77 to .2 VDC when the car is on at .116 mA.
The resistors are 10 ohm for my Passat I think.

The blue wires go to the circuit output. The o2 signal wire or black o2 sensor wire goes to the blue wires.

The brown wires go to the battery ground. The o2 sensor ground or grey o2 sensor wire goes to the brown wires.

The pink ones go to the resistors.
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File Type: jpg 100_9405.JPG (783.1 KB, 7 views)
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Old 13th July 2013, 03:33 PM   #28
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Hi,
Do you have the polarity right? I think the blue one it is the positive wire of the O2 sensor.
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Old 13th July 2013, 08:26 PM   #29
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Quote:
Originally Posted by tauro0221 View Post
Hi,
Do you have the polarity right? I think the blue one it is the positive wire of the O2 sensor.
The wire I used (blue in the pictures) goes to black wire on the O2 sensor harness (if I had one). I don't have black, grey or white wires, just using them as reference from standard O2 wiring. So blue goes to black. Grey is O2 signal ground, goes to brown wires and battery ground. The white ones are the O2 heater circuit. Those go to my resistors. Basically I don't know if grey (O2 signal ground should go to the battery). Also it's strange that I get code P0056, but not P0036 anymore. The circuit goes to both O2 sensor signal inputs, but I only get one code. I checked to see if they are wired correctly. I can tell they are because when you unplug one the voltage oscillation changes slightly.

I don't know what resistance the white wires should have wired in. The resistance in the O2 heater sensor seems to go higher that hotter it is.
8 ohms didn't work, then 10 didn't now I have 18 ohms for each circuit.
I measured one of the front O2 sensors and the resistance was 10.7 when warm and 14.5 ohm when pretty hot.
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Last edited by Jimmy154; 13th July 2013 at 08:29 PM.
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Old 13th July 2013, 08:54 PM   #30
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Hi,
Still I think the pin that it is alone from the rest in the connector it is were the O2 should be connected. Also if you do not have a right heater resistance the MCU will not recognized that the sensor it is connected.
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