Bench running a speedometer

So a couple weeks ago I bought a 94 jeep cherokee XJ for my GF to drive back and forth to work. I will also drive it every now and then too. Its a base model cherokee and on those the guage cluster only has a speedometer, fuel guage and then dummy lights for the rest. All the models above the base model have speedo with trip meter, tach, fuel, oil pressure, coolant temp, and volt meter. All you have to do is remove the base model cluster, plug in the better cluster, then change the oil and coolant sending units. Real easy swap. Its driving me nuts not having a tach and the other guages. I hate dummy lights.
So I found one in the local pull a part for cheap. Had like 272k on it. Well the cherokee I bought only has 150k. So being OCD and annal, I had to have the mileage right. So I dismantle the speedo and start trying to find a way to run the miles back. I found if I just spun the gear for the miles (its a electric speedo, but the miles are mechanical) by hand backwards it worked, but it was going to take forever. Long story short, I try a couple different ways of speeding it up (one involving a dremel tool) and lock it up from spinning it too fast :innocent2: :laugh: :mad1:
Fast forward a week and I have another cluster in my hands (from ebay). I lucked out and this one has less mileage. (135k) Since I paid a good bit moroe for this cluster (more than I really wanted), I dont want to screw it up (no taking it apart) It came with the pigtails from the wiring harness, so I used the wiring diagram and found the power and ground wires, also the speedo signal wire. I also have a spare speed sensor. Its a hall effect sensor, (8ppr) So I used a old computer power supply, used the 12 volt for the speedometer, and the 5 volt for the sensor. I can spin the speed sensor with my cordless drill and it works!

SO, heres my idea. What I would like to do is find a way to just run the speedo and let the miles naturally roll up on the cluster. The speedo maxes out a 85 mph. If I am reading the sticker on my drill correctly, it maxes out at 1400 rpm, this put the speedo at about 70mph. I have calculated out, that if I could run the speedo at 85 mph, it would have to run for 24 hours a day for a hair over a week to make the mileage correct. But naturally I cant use my cordless drill for this. The speed sensor has a square male shaft sticking out of it (same size as the old speedo cables) So here is where I need some help. I need to find some type of small electric motor I could maybe vary the speed on that I could somehow attach to the speed sensor. I have been thinking about what I could use and cant come up with anything. It doesnt have to be very big or powerful, as the vss is real easy to spin.
So, anyone have any suggestions?

For reference, here is a pic of the speed sensor I need to spin.

Attachment 7662

just generate the signal. the soundcard in your computer may be sufficient for this task.

Drill a hole just big enough for the square to fit in some round stock. Then drill / tap two set screws to lock the square inside the hole. Attach the drill to the round stock.

dave w

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Originally Posted by dave w

Drill a hole just big enough for the square to fit in some round stock. Then drill / tap two set screws to lock the square inside the hole. Attach the drill to the round stock.

dave w

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Why would you go through all that trouble when you can just insert the tang into a drill chuck?

ahhhh just generate the signal

i betcha you could just record the signal from the vss with the soundcard input, loop it, and play it on output

just dick around with the gain (volume) till it actually accepts the signal and moves the speedo

mechanical solution to electrical problem bad

Quote:

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Originally Posted by steveo

ahhhh just generate the signal

i betcha you could just record the signal from the vss with the soundcard input, loop it, and play it on output

just dick around with the gain (volume) till it actually accepts the signal and moves the speedo

mechanical solution to electrical problem bad

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Yep, that's definitely possible, though I would use a function generator if it were me. Sometimes the simple solution to some people is the mechanical solution. ;)

simulating a hall-effect sensor? a 555 can do that without any issue.

I am not the most computer savy person out there. Simulating the signal? How in the world would I even be able to do that. Would I need some type of special program? What would I hook to my computer to hook to the speedo? Would it be usb powered/operated? I would need some very detailed and very easy to follow instructions.

i have just done this im using a free signal generater to input rpm to my flowbench ecu so it will read maf soundcard is all you need 12kb download LOL i can set rpm to up over 9000rpm square wave
http://www.wavosaur.com/generatosaur/

i never see suggested schematics for any of those which makes me somewhat nervous about potentially overloading the sound card.... i know most/all are okay with 64 ohm loads, but i don't know how much lower you can go with impedance.

i've got an otherwise unused soundblaster laying around, but that would need to go into the desktop and i tend to need my testing stuff on my laptop.

im just straight in the jack nothing in between just straight to the crankshaft ref input that comes from the dfi normally and to the module earth wire that went to the dfi.been running connect for 6 hours over the last couple of days on 2 pc's.the soundcard scopes are the ones you want to watch out for you need a simple voltage devider inline to limit volts etc into the mic input or line in

Well I was talking about this to a co-worker yesterday and he mentioned he had a couple small 12v motors. One he said came out of a small cheap air compressor that plugged into the cig lighter, and the other he has no clue, but he thinks possiably a rc car.
So I fool around with them. The one from the compressor has a gear on the end I cant really use. The unknown one has some brass end on it that looked like it went inside a plastic gear at one time but broke. So its just kinda a round kunrled nub. I find a peice of vaccum hose would tightly slip over it, and then loosely slip over the speed sensor drive (but still enough to grip it) I find a old dimmer switch for the dash lights in a vehicle, I hook it up with the motor and 12v is spinning it way way too fast, even at the low setting. So I try 5v and it sounds more like it. I zip tie the motor and sensor to a peice of wood, wire it all up and give it a try with the broken cluster. Everything seems to be in order. So far its working. I dont have quite as fine of adjustment as I wanted using the dimmer switch, but I can get it up to around 75-80 mph, move it a fraction more and it goes past 80. Not sure I want to run it that fast. I used my multimeter and its putting about 0.8 volts to the motor to get it at the correct rpm. Anyone have any idea of maybe something else with a more fine adjustment I could use to adjust the voltage?
I'm gonna let it run for a few hours with the broken cluster and make sure everything keeps working ok then start on the good cluster.

Just to update for anyone who cares. It ran non stop all week and finally reached the proper mileage this afternoon. Did the swap and it was a sucess!