Electronics Guru's, I need your advice!

[Painless]

I've built a simple voltage adder that feeds a 1.5v AA battery through a 10k pot, the result is the ability to generate between 0 and approx 600 millivolts.

My intention here is to use this to add voltage to the signal from a narrowband O2 sensor. From my electronics days ( a long time ago! ) my head tells me that to add two voltages together you must connect them in series, however, if I take the signal wire from the O2 sensor and lead it into the ground from my AA then take the output from the pot and send that to the ECU, I will be applying resistance to the voltage from both sources which isn't what I want to do. I only want to apply resistance from the pot to the AA batteries output and then add that to the signal on the wire from the O2 sensor.

How would I wire this to achieve the above?

Thanks!

Russ.

[Riddler250]

I've built a simple voltage adder that feeds a 1.5v AA battery through a 10k pot, the result is the ability to generate between 0 and approx 600 millivolts.

My intention here is to use this to add voltage to the signal from a narrowband O2 sensor. From my electronics days ( a long time ago! ) my head tells me that to add two voltages together you must connect them in series, however, if I take the signal wire from the O2 sensor and lead it into the ground from my AA then take the output from the pot and send that to the ECU, I will be applying resistance to the voltage from both sources which isn't what I want to do. I only want to apply resistance from the pot to the AA batteries output and then add that to the signal on the wire from the O2 sensor.

How would I wire this to achieve the above?

Thanks!

Russ.

well yes you are right to wire in series. the pot will resist both, but adding the aa will help compensate for the loss of the o2 sensor. maybe you should use 2 AA batteries to compensate for the loss. just my 2cents. but im not sure if just adding the AAs will work how you imagine. Ive put thought into this as well instead of building a $50 efie. the timer was the reason i gave up. efies have an ic on the board that converts sine wave. its basicly a timer. I could be wrong. but ive talked to other techs here at the shop and that seems to be the consensus. Prove me Wrong please! it would be so much easier than a full blown efie.

[Jaxom]

Use your device to bias the sensor reference instead of the signal itself. By raising the voltage of the reference wire, you will "push" the signal voltage up by the same amount, without affecting the impedance or response of the sensor signal. Dodge does it from the factory (the newer Hemi trucks use a 2.5-3.5v O2 signal,) and I see no reason it wouldn't work on all 2- or 4-wire O2 sensors.

If your O2 uses a typical black-gray-white-white color code, the black is the signal wire and gray is the reference. Install your device in series with the gray wire, so that the (+) side is toward the sensor. Let us know how it goes.

[Painless]

Thanks for your input jaxom, boosting the bias wire instead definitely makes a lot more sense. I did get my circuit working on the signal wire this morning, but had to turn the knob all the way to make a small difference.

I'm going to give this the weekend, as I'm working, on monday I will switch to the signal wire.

By the way, my 2006 4.7 Ram has a four wire O2, wired as follows:

Blue: O2 signal to ECU
White: Bias from ECU
Two black wire: Heater, I'm guessing.

[Painless]

Ok, I gave my poor mans EFIE a test run on the way to work this afternoon. Firstly, my Rams O2 sensor seems to behave like this:

When you first switch on, the sensor feeds 0v, this slowly rises over about 10 seconds to 2.5v (the bias). The sensor sits at the voltage until it warms up, at which point it starts to oscillate with the oscillation getting stronger as it warms. When coasting or sitting still after stopping, the sensor tends to sit in the high voltage range on rich, although it will sometimes go back to oscillating after a while.

Going back to my circuit, I noticed that when the vehicle is switched on and is steadily climbing up to 2.5v that turning my pot has the desired effect of increasing voltage, however, once it has reached just over 2v the pot makes no difference whatsoever.

I'm currently using 2 AA in series to provide 3v to my circuit, I'm wondering if this just isn't enough considering the strength of the signal (with the 2.5v bias) on my truck in comparison to 0-1v systems where this circuit seems to work fine.

I'm considering finding a 5v voltage regulator somewhere (salvage) and using that to power my circuit and see if it makes any difference. I'm also considering Jaxoms suggesting of augmenting the bias line instead, although I think I will face the same issues with affecting the voltage.

[Riddler250]

Ok, I gave my poor mans EFIE a test run on the way to work this afternoon. Firstly, my Rams O2 sensor seems to behave like this:

When you first switch on, the sensor feeds 0v, this slowly rises over about 10 seconds to 2.5v (the bias). The sensor sits at the voltage until it warms up, at which point it starts to oscillate with the oscillation getting stronger as it warms. When coasting or sitting still after stopping, the sensor tends to sit in the high voltage range on rich, although it will sometimes go back to oscillating after a while.

Going back to my circuit, I noticed that when the vehicle is switched on and is steadily climbing up to 2.5v that turning my pot has the desired effect of increasing voltage, however, once it has reached just over 2v the pot makes no difference whatsoever.

I'm currently using 2 AA in series to provide 3v to my circuit, I'm wondering if this just isn't enough considering the strength of the signal (with the 2.5v bias) on my truck in comparison to 0-1v systems where this circuit seems to work fine.

I'm considering finding a 5v voltage regulator somewhere (salvage) and using that to power my circuit and see if it makes any difference. I'm also considering Jaxoms suggesting of augmenting the bias line instead, although I think I will face the same issues with affecting the voltage.

That was one of the issues i discussed with one of the senior techs here at work. except i wasnt thinking about the bias line(not to familiar with sensors). I agree with 2 AA's just not being enough, voltage on batteries like that vary too much and will drop power fast if any significant current is drawn from them. why not run power from a 12v source with resistors, throw in a cap as a filter and drop that down to 5v with your pot turned all the way up, then you should be able to drop it with your pot to the desired range. just a thought, i might be talkin out my rear, i havnt slept well in a few days, starting to notice.

[atfab]

I hope this works, if not try my photo site for a simple o2 adder.

atfab

it did!

[alpha-dog]

Use your device to bias the sensor reference instead of the signal itself. By raising the voltage of the reference wire, you will "push" the signal voltage up by the same amount, without affecting the impedance or response of the sensor signal. Dodge does it from the factory (the newer Hemi trucks use a 2.5-3.5v O2 signal,) and I see no reason it wouldn't work on all 2- or 4-wire O2 sensors.

If your O2 uses a typical black-gray-white-white color code, the black is the signal wire and gray is the reference. Install your device in series with the gray wire, so that the (+) side is toward the sensor. Let us know how it goes.

I have to tell you that on my 2006 dodge ram1500 with hemi that I tried both black and gray wires with fuel-saver EFIE. I am confused. On the gray wire I would get check engine lights alot, and on the black I used a scan gauge and my short term fuel trim never changed. WTF! I want to go on to the MAP mod but I feel that I should see something on the scan gauge. Isn't STFT a ECU reaction to what the o2's are telling it. Is there a better monitor to use.
Russ

[protecheqp]

getting kind of lost here but why use batteries when you in a circuit that provides 12 volts ? maybe ......... i miss read something......... just use a take off remember ohms law .........hell you could even use a pot ...

[Painless]

I have to tell you that on my 2006 dodge ram1500 with hemi that I tried both black and gray wires with fuel-saver EFIE. I am confused. On the gray wire I would get check engine lights alot, and on the black I used a scan gauge and my short term fuel trim never changed. WTF! I want to go on to the MAP mod but I feel that I should see something on the scan gauge. Isn't STFT a ECU reaction to what the o2's are telling it. Is there a better monitor to use.
Russ

If your ram is a 2006, then its a 3rd gen like mine. The black and gray wires are for the o2 heater, the white wire is the 2.5v bias and the blue is the signal back to the ECU.