Hi all, I need help...
I have fitted a new Ford engine and gearbox from a Ford Focus ST170 (SVT in the USA) that has a three wire Vehicle Speed Sensor (VSS) into my older Ford Orion that has a mechanical speedometer.
In simple terms I now need to read the signal from the VSS. Determine how many pulses is makes per mile, convert the pulses to a voltage to spin a dc electric motor or pmw to drive stepper motor. I can then use the motor to spin the mechanical input to the speedometer to display the correct speed.
Engine/gearbox transplants like this typically create this problem for a lot of 'car enthusiasts', so solving this problem would be very useful for loads of people. There are aftermarket products that solve this problem, for example see ECD-100 from Dakota Digital, but the cost is prohibitive.
As I understand it the VSS is a Hall effect device, the three wires provide a ground, 5vdc supply and signal. From other searches I have found out that the Ford VSS might produce 8,000 pulses per mile (or possibly 3.5 times this as per another search), but this will not be the case in my set up where tyre sizes have changed so I will need to calibrate the electronics.
The ECD-100 has a calibration mode where the car is driven a 'measured mile', I guess the number of pulses are then read and registered allowing the electronics to produce the 'corrected' revolutions of the motor.
I'd be happy using a potentiometer to increase, or decrease, the gain/voltage driving the motor - I would calibrate the speedometer by driving at a 'known speed' (use a SatNav with GPS speed on it) and adjust the POT so that the speedometer reads the correct speed at two or three points (e.g. 30mph, 60mph and 90mph). The mechanical speedometer reads 60mph when the input is running at 1,600rpm, so for my car the Electric motor needs to spin from 0rpm to 4,000rpm.
Can you help me? I'm an mechanical engineer so although I'm okay with connecting things up I'm new to electronics.
I have seen lots of posts about how to drive a motor, but nothing about how to read a signal, calibrate it and then spin a motor. I'd like to use 12vdc for the electronics (so I can plug it straight into the car battery without using a power supply) and use a cheap 0.5A 12vdc motor if possible, but you guys might tell different. Either way I'd like to keep it really simple.
Many thanks in advance, Clive
Ps I'm not really a Proffessor!
I have fitted a new Ford engine and gearbox from a Ford Focus ST170 (SVT in the USA) that has a three wire Vehicle Speed Sensor (VSS) into my older Ford Orion that has a mechanical speedometer.
In simple terms I now need to read the signal from the VSS. Determine how many pulses is makes per mile, convert the pulses to a voltage to spin a dc electric motor or pmw to drive stepper motor. I can then use the motor to spin the mechanical input to the speedometer to display the correct speed.
Engine/gearbox transplants like this typically create this problem for a lot of 'car enthusiasts', so solving this problem would be very useful for loads of people. There are aftermarket products that solve this problem, for example see ECD-100 from Dakota Digital, but the cost is prohibitive.
As I understand it the VSS is a Hall effect device, the three wires provide a ground, 5vdc supply and signal. From other searches I have found out that the Ford VSS might produce 8,000 pulses per mile (or possibly 3.5 times this as per another search), but this will not be the case in my set up where tyre sizes have changed so I will need to calibrate the electronics.
The ECD-100 has a calibration mode where the car is driven a 'measured mile', I guess the number of pulses are then read and registered allowing the electronics to produce the 'corrected' revolutions of the motor.
I'd be happy using a potentiometer to increase, or decrease, the gain/voltage driving the motor - I would calibrate the speedometer by driving at a 'known speed' (use a SatNav with GPS speed on it) and adjust the POT so that the speedometer reads the correct speed at two or three points (e.g. 30mph, 60mph and 90mph). The mechanical speedometer reads 60mph when the input is running at 1,600rpm, so for my car the Electric motor needs to spin from 0rpm to 4,000rpm.
Can you help me? I'm an mechanical engineer so although I'm okay with connecting things up I'm new to electronics.
I have seen lots of posts about how to drive a motor, but nothing about how to read a signal, calibrate it and then spin a motor. I'd like to use 12vdc for the electronics (so I can plug it straight into the car battery without using a power supply) and use a cheap 0.5A 12vdc motor if possible, but you guys might tell different. Either way I'd like to keep it really simple.
Many thanks in advance, Clive
Ps I'm not really a Proffessor!