I've connected an Acewell 7659 digital dashboard to a kit car, but I've been having trouble with the speed interface. The car has a Variable Reluctance sensor but the dash is only compatible with Hall Effect (a square waveform which alternates between +5V and -5V: the dash registers a pulse every time the voltage crosses 2.5V).
I've connected a VR to Hall converter but as the dashboard speed connection is outputting +5V I've been advised this may blow the converter if I connect it to the output. The dash has a strong pull-up resistor so adding a resistor doesn't work.
I've attached a circuit diagram of how it's all connected (in the diagram there's a zener diode connected between the output and ground - a friend suggested this, but it didn't work: without the dash connected it gave the correct output but when the dash was connected the output hovers around 4V).
What I need to know is how to connect a transistor between the dashboard and converter so as to protect the converter. I think this is probably a pretty basic connection but I'm not too good on electronics. I'm guessing I need two or three resistors but I have no idea what ratings.
Any help very gratefully received.
I've connected a VR to Hall converter but as the dashboard speed connection is outputting +5V I've been advised this may blow the converter if I connect it to the output. The dash has a strong pull-up resistor so adding a resistor doesn't work.
I've attached a circuit diagram of how it's all connected (in the diagram there's a zener diode connected between the output and ground - a friend suggested this, but it didn't work: without the dash connected it gave the correct output but when the dash was connected the output hovers around 4V).
What I need to know is how to connect a transistor between the dashboard and converter so as to protect the converter. I think this is probably a pretty basic connection but I'm not too good on electronics. I'm guessing I need two or three resistors but I have no idea what ratings.
Any help very gratefully received.