Lamda Sensor Heater Driver?

[kbs]

Hi,

Sorry - a cheeky enquiry as I'm currently not using a Megasquirt but expect to be upgrading to one by the end of the year. Before that happens, I want to use a Lamda sensor with a diy fuel system.

Using a Bosch LS602 basic Zycronia Lambda Oxygen Sensor (4 wire narrow band) in car that never had a Lambda sensor.

Can the heater be driven directly from battery voltage safely? (max 15v)

I appreciate 5 wire sensors need 'driver circuits' but this is a basic 4 wire narrow band sensor.

I've studied the bosch books but cant get a specific answer, they refer in general to 12-13v and state that AC is better - I can't tell if this refers to narrow or wide band though...

All advice greatfully received.

Keith

[seishuku]

Narrow band sensors is just a simple heater, just put switched +12v when the engine is running to it and call it done.

Wide band sensor requires a precisely controlled heater for correct oxygen pump operation, thus the controller circuitry.

[kbs]

thanks seis

Do I need to protect it against a failing alternator that might cause the voltage to rise to nearer 15v?

If most cars are simply fed from a charging battery (~14v) then I would expect it to be OK.

Have I got this right or do I need to ensure the voltage to the heater does not rise over 12v?


Thanks again

Keith

[kjones6039]

If most cars are simply fed from a charging battery (~14v) then I would expect it to be OK.

Agreed! My somewhat limited experience with heated (3 & 4 wire) sensors would indicate that they all operate at system voltage, without special protection.

I wouldn't worry about it!

Ken

[seishuku]

I guess it's possible that in some case if the alternator failed really badly, it could possibly blow the heating element... But narrow band sensors are cheap, not much on top of an alternator cost.

But if your electrical system suddenly spiked to 17+ volts, I'm thinking you'd have other worries.

[kbs]

Thanks very much.

Yes, understood that a failed alternator will fry lots of stuff.

Good to know that the sensors can be run without additional protection on a healthy system.

Time to see if I can drill & tap the exhaust manifold - if not then its time to weld a boss into the (horizontal) part of the front pipe.

Thanks again

[seishuku]

Well, with those sensors, it's not directly powering the sensor in the same way others are powered.
O2 sensors work on a oxygen exchange reaction, that reaction generates a voltage it self, but requires heat for it to work.

Just the heat from the exhaust stream is usually enough, but it takes longer for the sensor to heat up, thus the heater that's built-in to most sensors now.