# Motor Run Away Protection



## judebert (Apr 16, 2008)

That's exactly how I intend to set up the speed switch for my EV. The problem at the moment is finding a switch!

A quick Google search is not showing specs or sources for the ISSPRO 4901. Where are you going to obtain yours? Can I get one, too?


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## Jimdear2 (Oct 12, 2008)

Sorry, should have put a link in the last post. 

http://www.isspro.com/

Search 4901(or r4901). ISSPRO seems to be a high end custom automotive and truck gauge manufacturer.

For some reason the do not place spec sheets on their site. Try emailing Bill Larson [[email protected]] to get prices and specs.

Jim


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## TX_Dj (Jul 25, 2008)

This was being discussed over the weekend on the NTEAA mailing list.

The idea I pitched to the group was to take an electronic tach which accepts a hall-effect input (most of the newer electronic tachs do), which is also equipped with a "programmable shift light". You can then tap the shift light circuit to drive other components to drop the main contactor or other shut-down means if the programmed RPM is exceeded.

*shrug* Haven't done it, but it seems plausible.

Also, if your motor is rated for your max voltage (i.e. you're not overvolting the motor), then you can never overspeed it unless you're towing it in too low of a gear with the driven wheels dragging the motor over its redline.


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## Jimdear2 (Oct 12, 2008)

The Tach and shift light were my first go round idea as well for runaways, see my thread "An Electric Pulling Tractor" under "EV Conversions and Builds" I go into what I wanted to do in some detail.

I just couldn't find the mechanical relay that would remain open until it was deliberatly reset. I admit though, that I hadn't done much research when someone brought the ISSPRO speed switch to light. 

I may still do the research because the speedswitch is $225.00. I would much rather use the Tachometer/shift light to trip a manually resetable relay that is right in the main contactor control circuit.

I could swear that I read in some threads that people had overspeeded their motors when coasting downhill with a directly connected setup or ones that were left in gear. I was thinking that the unlatched speed switch could be used to engage some form of braking or warning system when a trip speed was reached, then disengage when the lower limit was reached. 

Jim


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## TX_Dj (Jul 25, 2008)

Two options come to mind...

First is a normally-closed relay in addition to the normally-open relay used for your KSI. The normally-closed relay acts like a switch that's "ON" unless the coil is energized, and then it's like a switch that's "OFF".

Another is a latching of "pick" relay. You can engage it with a trigger from the "start" position on the key switch, and you can disengage it with a trigger from the shift light circuit. The caveat here is "picking" the relay to release when you turn the key to the "off" position.

Other methods are available as well, I'm sure.


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## judebert (Apr 16, 2008)

Personally, I'm liking the ISSPRO r4902. It's got two adjustable set points for the outputs, which include both NO and NC sides. I think I'll wire the first one to turn on a light or buzzer (or both!), and the second to interrupt power to the contactors, shutting the whole car down.

It won't protect me from down-shifting idiocy, or rolling retardation... unless I wire something to engage the clutch, too. Hmmm.... all I'd need would be a relay and a solenoid, right?


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## Jimdear2 (Oct 12, 2008)

Sounds like you are on the right track, I wont be there until spring (I have to work outside) so if you do it, post the results.

Jim


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## ElectriCar (Jun 15, 2008)

Is this sensor what you guys are looking for? I just stumbled upon it this week.


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## Jimdear2 (Oct 12, 2008)

This is exactly the sensor that D&D Motors sent me. Looks like there are at least two options for some motors now.

Jim


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## TX_Dj (Jul 25, 2008)

I found out that MSD makes a series of modules designed to trip once an RPM is exceeded, or between an RPM "window". I.E. the first would click a relay if X RPM is exceeded, and the second would click a relay one X RPM is exceeded and release once Y RPM is met.

They're used for things like activating nitrous systems within the powerband, but releasing nitrous before the redline is hit. (Nitrous + rev limiter = bad mojo on the engine)

Maybe something like this could help too. I think summit sells the first type for $99.


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## ElectriCar (Jun 15, 2008)

jimdear2, what did you connect your sensor to?


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## Jimdear2 (Oct 12, 2008)

Great!!!

It sounds like everyone is finding RPM limit switch options now. 

The MSD switches TX_DJ found sound similar to the ISSPRO speed switches my freind origanally found. I will look at those as well.

To answer Elecrticar's question, I'm not sure what you are asking so I'll give two answers I think are right.
I will be mounting the hall sender into a purpose built pocket on the back end of the D&D motor. 
I will either be connecting the hall sensor (with the required pull up resistor) 
to an Autometer brand (or equivalent) 5 inch 11,000 RPM Recording Tachometer with setable shift light to control a mechanical latching relay 
or directly to an electronic speedswitch without a Tachometer. 

1.) Using the Tach, Shift Light and Mechanical Latch Relay; 
The hall sensor will drive the tachometer, using the built in setable shift light function, a safe RPM limit is set into the tachometer. A mechanical latching relay (about 15 -20 dollars) is set into the contactor control circuit the and is set normally closed when power is switched on. The hope is that when the safe RPM limit is reached the tach light signal will be sufficient to trigger the latching relay to it's latched normally open mode which will open the main contactor and sut down the motor. Potential problems: 
(a.) Is the shift light pulse strong enouch to trigger the mechanical latching relay.
(b). Is the mechanical relay fast enough to shut everything down in time.
(c,) Is a mechanical relay reliable enough.

2.) I will use the electronic speed switch r4901, or equivalent, set in its latching mode. 
The pulse count per counted RPM and the RPM breakpoint will be set by ISSPRO to your spec. The speedswitch in this mode, as I understand it, is set to be normaly closed when initially powered this normally closed circuit will be used to power the main contactor circuit (The ISSPRO speedswitch doesn't pass enough current to directly control the main contactor actuating circuit so an additional relay will be required. I will check the other mentioned switches to see if they will). The hall sensor will supply the speedswitch with the required RPM signal.
Potential problems: 
(a.) The r4901 switch is set by ISSPRO and I assume must go back if any change is needed.
(b.) The r4901 speedswitch will require an additional relay or electronic switch to control the main contactor circuit. 
(c.) There is no way to check if the system/set point are correctly functioning without tripping the system, scary if it is not.

I had planned on doing some testing this weekend but the doctors had to have there way with me again for a couple of days so I didn't get things ordered. I am ordering the latching relay today and hope to mount the hall sensor with pull up resistor, tach and latching relay breadboarded to the motor soon. I'll run the motor at 12v to see if I get signals and see if I can get the relay to trip at a set RPM.

I'll post the results when I "Get er Done".

Be well,
Jim

P.S. 
By the way both the electronic and mecanical latching switch/relay have normally open contacts that are closed when the switch latches open. These contacts when closed could tuen on a light or buzzer to let you know that the runaway system just tripped.
Also both systems will reset to normal by turning off the the main switch and then turning it back on.


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## kugmo (Oct 31, 2008)

protection system for a Motor, that would be a good idea, post some pictures if your finished with your project...


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