Electric Speedometer w/magnetic pickup off of driveshaft
As some of you may know, I changed to the fast lane west aftermarket gauge cluster and some autometer gauges in my Duster. It ended up looking like this:
Everything worked right out of the box, but I needed to have a sensor for the speedometer. I tried the type that screws on to where the speedometer cable goes (Chevy and Mopar are the same BTW), but my speedometer takeoff kept eating the plastic gears on my 4-speed. So, that way was out. I knew that some aftermarket cruise control units have a pickup and magnets that attach to the driveshaft, and I figured that would work alright since the autometer speedometer can be recalibrated for how many pulses per mile you need, and it can be calibrated an indefinate amount of times.
So, after buying the $24 Rostra magnetic VSS http://store.summitracing.com/partd...rt=RPC-250-4165&N=700+317078+115&autoview=sku
I hooked it up, glued the magnets to the driveshaft, and tried it out. It worked great above 30mph but liked to sit at zero at the lower speeds. Now, I remembered from the Electrical Engineering class I had that this type of sensor output an AC signal...which the autometer speedometer could read, but required a minimum voltage, and voltage increases with the feed rate of the magnets. This left me with two options...add even more magnets which might not work, or find an AC sine wave to DC square wave conversion module.
After some reading online I found that many late 80's GM vehicles use something called a VSS Buffer Module (or sometimes a DRAC) that would accomplish the AC to DC conversion for me. So, today I went to the local pick-your-part junkyard and got the VSS buffer out of an 89 Firebird.
I made a web page showing the wiring and steps I took:
http://duster318.freeservers.com/tech/VSS/universalvss.htm
I can tell you that the speedometer now functions perfectly down to 5mph. Now I just have to fix the exhaust leak and do some minor tuning and it will be totally road ready and road legal.
Thought some of you might be interested. This would be hard to figure out on your own! :-)
As some of you may know, I changed to the fast lane west aftermarket gauge cluster and some autometer gauges in my Duster. It ended up looking like this:
Everything worked right out of the box, but I needed to have a sensor for the speedometer. I tried the type that screws on to where the speedometer cable goes (Chevy and Mopar are the same BTW), but my speedometer takeoff kept eating the plastic gears on my 4-speed. So, that way was out. I knew that some aftermarket cruise control units have a pickup and magnets that attach to the driveshaft, and I figured that would work alright since the autometer speedometer can be recalibrated for how many pulses per mile you need, and it can be calibrated an indefinate amount of times.
So, after buying the $24 Rostra magnetic VSS http://store.summitracing.com/partd...rt=RPC-250-4165&N=700+317078+115&autoview=sku
I hooked it up, glued the magnets to the driveshaft, and tried it out. It worked great above 30mph but liked to sit at zero at the lower speeds. Now, I remembered from the Electrical Engineering class I had that this type of sensor output an AC signal...which the autometer speedometer could read, but required a minimum voltage, and voltage increases with the feed rate of the magnets. This left me with two options...add even more magnets which might not work, or find an AC sine wave to DC square wave conversion module.
After some reading online I found that many late 80's GM vehicles use something called a VSS Buffer Module (or sometimes a DRAC) that would accomplish the AC to DC conversion for me. So, today I went to the local pick-your-part junkyard and got the VSS buffer out of an 89 Firebird.
I made a web page showing the wiring and steps I took:
http://duster318.freeservers.com/tech/VSS/universalvss.htm
I can tell you that the speedometer now functions perfectly down to 5mph. Now I just have to fix the exhaust leak and do some minor tuning and it will be totally road ready and road legal.
Thought some of you might be interested. This would be hard to figure out on your own! :-)