# Tachometer module for NetGain motors



## david85 (Nov 12, 2007)

I can't believe no one commented on this yet! This would be a great idea. Does he have a website? Any pictures of the device?


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## gdirwin (Apr 7, 2009)

Is it this device?










from:
http://rechargecar.com/product/warptm-speed-sensor


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## Tesseract (Sep 27, 2008)

gdirwin said:


> Is it this device?
> ...
> from:
> http://rechargecar.com/product/warptm-speed-sensor


Josh at Recharge Car contacted me last week to see if his pickup would work with the Soliton1's tachometer input, so I told him to send me one and I'd find out.

He said it uses a Hall effect sensor, but with a biasing magnet inside so as to better tolerate stray/incident magnetic fields. We shall see...

I personally prefer using inductive or retroreflective optical prox sensors for the tach pickup, especially near a big bad DC motor's field structure, but if his gadget works it's a reasonably priced "turnkey" alternative to cobbling together your own out of industrial automation parts.


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## DONEAL (Sep 10, 2008)

This is a better price that the one at evparts.com their’s is about 171.00.
However you can build one yourself, I did. I had problems using the hal-effect sensor. It could have been a bad sensor, not sure, I just had the one sensor to use. Never did get it to work.
I did get the glass reed switch part # rsw-27 at .50c each min order two to work. I also purchased Press fit magnet switch # ms-11 at 2.75 each and it worked as well. both from http://www.allelectronics.com/
I bench tested both, I decided to use the magnet switch.
Purchase magnets from K&J magnets inc. ¼” dia. X ½ “ axially neodymium cylinder magnet n42 at .70 each. 
Purchased ¼ “ x 2” npt brass nipple at 1.29 local hardware store.
Purchased two nuts and ¼” Brass collar at 1.49 local hardware store.
Purchased two ¾ “ 10-32 nf allen set screws both at .98 local hardware store
Aluminum Collar made from scrap left over from adapter plate 
Aluminum 1 ½ x 1 ½ x 2 “ long angle from scrap
Steps to build
1. I used a drill with a 2 ½ “ hole saw to cut out the alum. Collar ( size was what the scrap piece allowed)
2. I used a drill with a 19 mm hole saw to cut out the inside hole of the alum collar. (the size of the tail shaft on my motor)
3. I used a drill with a #21 drill bit for the two set screw holes. Then tap them for the ¾”set screws. ( could have used shorter set screws, but didn’t want to take any chance of striping out the threads when I tighten them.)
4. I use a drill with a ¼ “ drill bit for the two magnets. Used glue to hold the magnets in the hole, I did turn magnet poles, one north and the other south. ( really didn’t mater, the magnet switch would work with the magnet poles in either direction.)
5. For the alum. Bracket I use a drill with a ½” drill bit to make the hole for the brass nipple ( note the O.D. of the nipple is ½ “ so I had to woller out the hole a little so the nipple would fit)
6. Pushed the press in magnet switch into on end of the brass nipple then filled the other end with silicone rubber sealant. 
Cost to build 14.21$
Time spent to build about 3 hours
I would insert a picture here but I dont know how.


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## JRP3 (Mar 7, 2008)

Nice DIY! Can't beat the price.


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## Tesseract (Sep 27, 2008)

DONEAL said:


> ...I had problems using the hal-effect sensor. It could have been a bad sensor, not sure, I just had the one sensor to use. Never did get it to work.


Not surprising... Hall effect sensors produce a voltage in response to the strength of a magnetic field. Unfortunately, running hundreds of amps through the motor wires creates a very strong magnetic field that is not contained at all, and even the motor itself will radiate a lot of uncoupled flux after it enters into saturation. A Hall effect sensor, then, is a particular poor choice for a tachometer sensor except if it is "pre-biased" by placing a magnet right next to it and then orienting the target magnet to the opposite polarity.



DONEAL said:


> I did get the glass reed switch part # rsw-27 at .50c each min order two to work.


Did you connect that to your vehicle's tach or is it feeding the tach input of a motor controller? The reason I ask is because reed switches, like all mechanical switches, bounce, so what you think is the switch turning on once when the magnet passes by may actually be dozens of closures. An analog tachometer won't care, but a digital one, and most (all?) controllers will.

Just an FYI.


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## Dave Koller (Nov 15, 2008)

This is what I did on the Saturn ADC motor - cost of pickup is around 20 bucks - very immune to noise - might need a pullup on some inputs - gear can be handmade (without mill machine ) -- In the Saturn 60 degree equal 6 lobes for the 6X to direct feed to the Tach (AROUND the PCM)... I'm sure you have seen me post it before BUT on another Saturn... 

P.S. It"s a Cherry speed sensor buy at Allied Electronics or for a bit more digi-key...

http://www.diyelectriccar.com/forums/showpost.php?p=151836&postcount=37
is abit more on the internal makeup of the sensor... built in noise supression...


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## DONEAL (Sep 10, 2008)

Tesseract said:


> Not surprising... Hall effect sensors produce a voltage in response to the strength of a magnetic field. Unfortunately, running hundreds of amps through the motor wires creates a very strong magnetic field that is not contained at all, and even the motor itself will radiate a lot of uncoupled flux after it enters into saturation. A Hall effect sensor, then, is a particular poor choice for a tachometer sensor except if it is "pre-biased" by placing a magnet right next to it and then orienting the target magnet to the opposite polarity.





Tesseract said:


> ....................................................................................
> Good point! but I think it was a bad sensor.
> 
> 
> ...


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