Normally Open Reed Switch as ebrake.

Sunder

Sunder

10 MW
Joined
Sep 6, 2011
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Location
Sydney, Australia
Guys,

I followed izeman's build thread with quite a bit of interest, since I found my controller doesn't support the hidden wire brake sensor, especially his part about his reed switch brake. Not quite sure I understood how it worked, but he asked me to start a new thread with photos of my own brake assembly.

The only reed switches which I can find that are small enough to fit on brake, are closed when the magnet is near, and open when no magnet is near - The opposite of what I thought we would need for a switch based ebrake. On my controller, when the circuit is open, it allows power...

So, here's the photo of my brake assembly. Any suggestions on how to build in a reed switch to kill power when I pull the brake lever?

IMG_0495.JPG

IMG_0496.JPG

Thanks.
 
looool. you got a mechanical DISC brake :) that's soooo easy. there are switches made for that.

pic borrowed from bmsbattery.com webpage:
hwbs-hidden-wire-brake-sensor.jpg


just insert in the bowden wire, connect to your controller, and you're done. 5min work. no need for reed/hall switches. works really well.
i built my solution only because those magura hydraulic in-line switches are expensive and not very reliable.
if you can't find any, pm me: i have one spare left.
 
izeman said:
looool. you got a mechanical DISC brake :) that's soooo easy. there are switches made for that.

pic borrowed from bmsbattery.com webpage:
hwbs-hidden-wire-brake-sensor.jpg


just insert in the bowden wire, connect to your controller, and you're done. 5min work. no need for reed/hall switches. works really well.
i built my solution only because those magura hydraulic in-line switches are expensive and not very reliable.
if you can't find any, pm me: i have one spare left.
Click to expand...

Yeah, the whole problem arose because my controller won't support the hidden wire brake sensor. Those things are three wire hall sensor based. Mine is two wire switch based.
 
It is likely that your controller has pads for either kind of brake wire (active low or high). Alternately, you can run the 5V wire from your throttle line to the hall-type brake lever, and it will then probably work fine using the ground wire from the two wire brake line as ground on the hall, and signal from the hall to signal on the two wire brake line. (you may have to move the signal wire inside the controller from the active low to the active high pad, or add an inverter)


But if you do want an NO reed for ebrake, they do exist; should be orderable from Mouser, Digikey, Farnell, etc. There are also even some security systems that use them, where they ahve two sensors--one for Closed and one for Open position of the secured entrance or window. Some very old computer and calculator keyboards also use them.


But you can use a NC reed as a brake switch, too, by putting the reed on the open cable stretch, and a magnet near it where it will engage the switch when you pull the cable enough.

Remember that neo magnets hold their fields close so they have a relativley small activation area, while ceramic magnets have a wider field so have to be moved farther away from the reed to deactivate.
 
Thanks Amberwolf. I can see that's possible, but it sounds a bit fragile to me. I'm thinking a 1mm tactile switch might be a more reliable solution.

TBH, I'm even thinking of totally replacing the controller with one that supports the HWBS, or just running no ebrake at all, but I don't know how dangerous that is.
 
I had a bunch of links about the ebrake cutoff switch but these are all I can find for now. As stated in earlier posts the reed switches are available in N.O. or N.C. flavors. There are a few three wires that do both around as well. Hope this helps a bit.

http://endless-sphere.com/forums/viewtopic.php?f=16&t=11760

http://endless-sphere.com/forums/viewtopic.php?f=3&t=31503&hilit=reed+switch

http://endless-sphere.com/forums/viewtopic.php?f=3&t=38848&start=30#p691975
 
Sunder said:
or just running no ebrake at all, but I don't know how dangerous that is.
Click to expand...
WIth a brushless motor, it's not, as long as your physical brakes can overpower the motor and stop the wheel anyway. It just runs the risk of damaging the motor or controller in an emergency situation like a physically broken throttle where you can't get the motor to stop.

But an "ignition" switch would fix that, too, doing hte same thing the ebrake does, essentially turning off the controller. (assumign you don't have regen enabled).


Only with a brushed motor do you really need to worry about runaway conditions becuase of a shorted controller, and an ebrake won't help you in that situation anyway. ;)
 
Sunder said:
izeman said:
looool. you got a mechanical DISC brake :) that's soooo easy. there are switches made for that.

pic borrowed from bmsbattery.com webpage:
hwbs-hidden-wire-brake-sensor.jpg


just insert in the bowden wire, connect to your controller, and you're done. 5min work. no need for reed/hall switches. works really well.
i built my solution only because those magura hydraulic in-line switches are expensive and not very reliable.
if you can't find any, pm me: i have one spare left.
Click to expand...

Yeah, the whole problem arose because my controller won't support the hidden wire brake sensor. Those things are three wire hall sensor based. Mine is two wire switch based.
Click to expand...
Your controller does support the hidden wire brake switches, but you have to do a bit of extra wiring. There's three wires on the hidden wire switch, normally red, black and something else. The red one is for 5v, which you can run into the controller or splice into the red for the throttle. Then, the same with the black. You now want to look at the brake switch connector/s on your controller, which are referred to on any wiring diagram as the low voltage brake switch connector. It's the same one as what you connect the normal e-brakes to. There's two pins: one is 5v and the other is 0v. You connect the 5v one to the third wire of the hidden wire switch.
To summarise: splice the red and black to the throttle red and black, then connect the third wire to the hot pin in the brake connector.
 
I'm guessing all that is in effect trying to use convince the controller the circuit has closed, when what we're actually doing is just giving it 5v from elsewhere?

I think for now, I'm happy to run without an eBrake. It's only a Q100 motor, despite having a powerful controller, and there's a kill switch on the throttle if anything goes wrong. Although really, with that little power, unless something goes wrong when I'm *already* doing 40km/h+, I should be able to reasonably safely lay the thing down. Hell, it's not like I haven't had a few low sides on my motorcycle before.

The thing is, everyone talks about NC reed switches, but I'm fairly convinced they don't exist. The few I have seen are actually wrongly described (They're actually normally open, but incorrectly described as normally closed). The closest I've seen is Cross Over - You have three pins out, and you decide whether it's normally open or normally closed depending on the pins you chose. However, those seem to be at least 55mm long, which is too big for my application, unless it's one set in glass:

4704699.jpg


I have considered something like that, and just covering it over with epoxy to protect it. I may still do that, but first, I want to try to put my bike on full throttle, then apply the manual brakes and see how much I can slow a motor with a (simulated) stuck throttle. If I can mostly stop the bike, I'll just forget the whole eBrake idea.
 
I don't think a Q100 is capable of enough torque to even slightly contribute to overpowering a decently setup brake before tearing itself apart. I can hall it down to a stall (around 15 amps) with pinky finger levels of effort. To be clear, I'm saying the heat and torque the Q100 can put into the brakes is such a negligible fraction that I think you could ride around with it wide open never letting off, and it would smoke the motor before it smoked the brakes, and you will still be endo limited on deceleration with a front or rear mounted motor.

In fact, on a normal upright bike, a rear hub motor of much higher capacity could still be overcome in a panic situation without anything more than a little ungraceful dismount, because the front brake should be able to lift the rear tire off the pavement right down to motionless.

Seriously. Try it. Get going fast, then, with the throttle off, do a panic stop down to 5 mph or so. Do it again with the motor wide open. I bet the most noticeable difference is that it feels weird to hold the throttle while braking.
 
Sunder said:
I'm guessing all that is in effect trying to use convince the controller the circuit has closed, when what we're actually doing is just giving it 5v from elsewhere?

I think for now, I'm happy to run without an eBrake. It's only a Q100 motor, despite having a powerful controller, and there's a kill switch on the throttle if anything goes wrong. Although really, with that little power, unless something goes wrong when I'm *already* doing 40km/h+, I should be able to reasonably safely lay the thing down. Hell, it's not like I haven't had a few low sides on my motorcycle before.

The thing is, everyone talks about NC reed switches, but I'm fairly convinced they don't exist. The few I have seen are actually wrongly described (They're actually normally open, but incorrectly described as normally closed). The closest I've seen is Cross Over - You have three pins out, and you decide whether it's normally open or normally closed depending on the pins you chose. However, those seem to be at least 55mm long, which is too big for my application, unless it's one set in glass:

4704699.jpg


I have considered something like that, and just covering it over with epoxy to protect it. I may still do that, but first, I want to try to put my bike on full throttle, then apply the manual brakes and see how much I can slow a motor with a (simulated) stuck throttle. If I can mostly stop the bike, I'll just forget the whole eBrake idea.
Click to expand...


Yes, you will be able to stop the bike your motor will not overpower your brakes. But you can trash a geared motor pretty quick if it is pushing against the brakes when it's wide open. So, in the end it's a safety item for you and for the motor as well. Glass reed switches are very common. It is what I used with the wires cut short and in several layers of heat shrink. Or, wire it up, stick it in a straw, plug one end and add epoxy for something a little better. DD motors will take quite a bit more of this kind of abuse before they are damaged.
 
If you want to use the pedal sensor, you need a brake switch because the power continues for a bit after you stop pedalling. You can overcome the motor power with your brakes, but it makes it feel like your brakes aren't working and doubles the braking distance. If yoy have brake cables, it's a five minute job to fit one of those hidden wire brake sensors, so what's the problem?
 
d8veh said:
If you want to use the pedal sensor, you need a brake switch because the power continues for a bit after you stop pedalling. You can overcome the motor power with your brakes, but it makes it feel like your brakes aren't working and doubles the braking distance. If yoy have brake cables, it's a five minute job to fit one of those hidden wire brake sensors, so what's the problem?
Click to expand...


Not disagreeing with your conclusion to use brake sensors, but you really need better brakes if a Q100 can impact your braking distance.
 
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