How do I prevent a voltage source from stealing from AA batteries?
Hello everyone,
I'm making an "idiot light" for a couple of engine sensors in my engine compartment. The "idiot light" will be on the Mass Air Flow and Throttle Body sensors. I'll be switching out to dual intakes (which will be including larger Mass Air Flow sensors and Throttle Body senors on each intake) and I'm making this so that I know if the secondary intake is active. The sensor voltage is a constant 2V DC.
What I made was two simple AA batteries in series, with the negative side of the AA battery going to the MAF signal wire (which outputs 2V DC). The positive side of the battery goes to the positive side of a 2.1V 20mA Green LED, and on that same lead the negative side of the LED is going to the MAF ground wire.
If I touch the two wires on the battery, it's super bright. Measuring the DC voltage between the two LED pins, I'm getting 2.8v to the LED. Here's where my problem comes in: When I connect the "idiot light" to the MAF sensor, the LED lights up EXTREMELY dim, so dim that you can't really see it at all during the day time. I checked the voltage at the LED pins and it's getting 1.9v to the LED. What I'm thinking is that the MAF sensor is stealing my AA battery voltage.
When I ground the positive side of the AA batteries (which is now the negative side of the LED pin since the LED is on this lead) to the MAF ground and then ground the negative side of the AA batteries to the vehicle (instead of the MAF signal wire), it goes extremely bright due to a complete circuit. But, as soon as I connect the negative side of the AA battery to the MAF signal wire (keep in mind that the MAF signal wire is hot with 2V DC), the LED goes extremely dim and measures 1.9v between the LED pins.
So, what's a simple way to prevent the AA batteries voltage from flowing into the sensor? I've tried to play with some 1N4001 diodes but can't seem to get anything to work!
Again, I'm making this so that I know if the secondary intake is active so I'd really like to get this working! I'm a complete idiot at electronics and circuity in general, so laymen terms or pictures would help a ton!
Thank you for ANY help!