We have built a paragliding winch, using a wrecked automatic 125cc scooter. The scooter is controlled remotely via a R/C model aircraft radio system and operated by the pilot. I have built a load cell which measures the line tension and prevents the line from exceeding a preset level. All the electronics are done, boxed and code written.
For various logic reasons, I need to detect if the scooter motor is running. I propose the following solution and am looking for guidance here please
The scooter has an alternator which charges it's battery (pretty dirty output I would imagine)
I intend to tap into the output of the alternator, rectify if required, and pump the output (12-15V) into a 7805 5V regulator.
The output of the 7805 will then, via a Optical Coupler (4N25X) feed into the UNO where I can monitor it's condition.
This sounds like a workable solution to me, but I was wondering if the group has any comments / alternative suggestions
So it seems you need to get before the rectifier the alternator regularly uses, right? I think you can simplify this by just using a small rectifier diode like 4007 followed by a resistor and a capacitor to ground (to smooth it out) and then the input diode on the OptoCoupler. Resistor value needs to be right to get reasonable current into optocoupler.
I would go with PeterH's idea as it is the simplest and so most reliable.
You could add an extra resistor between the junction of the other two and the arduino pin with a zener diode between the adruino pin and ground if you are really paranoid.
terryking228's idea would protect the arduino because of the opto-coupler.
Hi, Not sure how much and how reliably the battery voltage would represent if the motor is running or not.. Maybe fine if you can characterize it and then set the decision point in software.
In the Old Days before alternators, car "generators" had a relay that pulled in when the engine was running and spinning the generator. So the voltage at the generator output terminal was zero when the engine was stopped and 12V or 24V or whatever when it was running. I used that to determine when the engine had actually started on big diesel generator sets used as backup power for broadcast stations. Transistor logic and UniJunction Transistors for timing. An arduino would be SO much easier and better.
The diode right on one of the alternator output windings would have the same zero-to-something characteristic.
It appears the lights on the scooter do not come on until the motor is running!!! And as they are 13.5v DC while charging a 63K and 37K resistor chain will work fine (or nearest preferred values)
terryking228:
Hi, Not sure how much and how reliably the battery voltage would represent if the motor is running or not.. Maybe fine if you can characterize it and then set the decision point in software.
Easy enough to measure it. But if the lighting circuit is only live when the motor is running, that gives an obvious solution. (I guess you will want to disconnect the lamps because the load they add could be considerable on a small motor.)