Spa Design Hall Effect Wheel Speed sensors on DL1

[marck_c]

Hello,

I have four Spa Design Hall Effect Sensors which I am attempting to use as wheel speed sensors on my DL1 Logger. The SPA sensors have 3 wires: red (which I presume is 12/5v+); black (not sure if this is signal out or ground) and a plain shielded wire.

Initially I wired them into the DL1 with the Red wire receiving 5v+ from the DL1's 5v+ Ref Out, the shielded wire to DL1 GND and the Black to the DL1's frequency input. This did not work.

Does anyone know the correct way to wire these sensors?

I later tried intermittently connecting 12v+ to each of the frequency inputs on the DL1 and monitoring the inputs with the Monitor Software, reading Pulse counts 1 thru 4. When this is done the count figure immediatly jumps to a very high number 1,000,000 +, and then starts counting the pulses accurately.

Is there any way to prevent this?

[osborni]

If it's two wire, then it is probably operates like a switch. Passing a magnet by it will close (or open) the switch.

If it's a three wire sensor, the shield is likely the ground. So put 5VDC to the red, ground the bare wire and see if you get a signal by passing a ferrous target or a magnet by the head. Some of the three wire sensors require a resistor to work properly - look at R-T's Knowledge base.

You should be able to test it on a bench rather then going through the trouble of installing it on a car and messing with it there. A power supply (I use a surplus computer ATX power supply - gives me 3.3, 5 and 12 VDC for doing bench testing) and a volt meter should be all you need to figure it out.

That said, you really should try to find the data sheet from SPA. A lot of the automotive DAQ companies re-label sensors from the manufacturer. It wouldn't surprise me if the sensor is really a Cherry or a Honeywell.....

[marck_c]

I've searched the web and have no luck finding any data on these sensors. For what it's worth they look like this:

[osborni]

Just guessing, but Pegasus also sells magnets with the sensors as spares. They are probably magnetic reed switches. put an ohm meter to the red and black lines, then pass a magnet in front of the head (need to try both poles of the magnet) and see if you get a response.

You could also email SPA Technique to see if they will send you a manual - or call Pegasus to ask.

[marck_c]

I'll give that a try. Do these sensors need special magnets to work? Or will any type do?

[marck_c]

Tried checking with an ohmeter placed between the red wire and black wires. Applied a magnet and noticed no difference in the reading (open circuit)

[marck_c]

Got it figured now. The black is ground, red power, and the shielded wire the signal. It does need a magnet to trigger it. Normally it reads 3.2v and when the magnet passes it, it drops to 0v.

[osborni]

Good to hear - odd that the signal is the shield - but if it works, that's all that matters.

[marck_c]

Seems I spoke to soon. Still having problems. I had the voltmeter set incorrectly. I am getting a 0.3v drop to 0v when a magnet breaks the field. This is not enough to trigger the pulse for the DL1. Any ideas?

[marck_c]

Seems I spoke to soon. I set the voltmeter incorrectly. I am getting a 0.3v output with no magnet, and 0v with the magnet. This drop is insufficient to trigger a pulse on the DL1. This is with either a 12v or 5v input to the DL1. Any ideas?

[osborni]

other the trying to get a spec sheet for the sensor from Pegasus or SPA technique, all you can do is try all the combinations of wiring....

You could also use a different sensor. I've had good luck with Cheery. Not very expensive either.

http://www.race-technology.com/forum/vi ... php?t=1794

[marck_c]

Where can I purchase the Cherry sensors?

[osborni]

Digikey - about $32 each.

[marck_c]

Got the spa design ones to work today. Green = Ground (damn english!), red = +5v and black = signal. Had to put a 1k ohm pull up resistor between black and red. Also needed a rare-earth magnet as a target.

My only problem is I am getting a speed spike on the Dash2 moh readout. Not sure if it's interferance or what. I have the car jacked up and in gear running, with the speedo steady at ~15mph and it will jump intermittently to ~36 mph. Will investigate tommorrow.

[osborni]

Got the spa design ones to work today. Green = Ground (damn english!), red = +5v and black = signal. Had to put a 1k ohm pull up resistor between black and red. Also needed a rare-earth magnet as a target.

My only problem is I am getting a speed spike on the Dash2 moh readout. Not sure if it's interferance or what. I have the car jacked up and in gear running, with the speedo steady at ~15mph and it will jump intermittently to ~36 mph. Will investigate tommorrow.

signal noise? You could also play with the "Max rate of change" and the "Number of samples to average over" setting on the dash to quiet it down. I have the same issue. Every 10 minutes or so, the speed will spike or drop. Honestly don't ever notice it on the track though.

I only really use the wheel speed for the odometer street legal requirement (which I turn off on the track) and for data analysis, not for speed output. I use GPS for that.