9 replies to this topic

[SirBrass]

So I wired up a motor braking circuit in my rewired stryfe. Well, I notice that when braking I can see a flash of arcing beneath the motor caps (blade 180s). I don't want to wear out my motors but taking 5 seconds to spin down is annoying. Any ideas on how to gradually deliver braking current upon trigger release without using pwm & a board? Inductor in line on the braking lead to the negative line? And calculations on what inductor to use?

I really don't want to reduce my motors' life to a span of hours.

Edited by SirBrass, 02 March 2017 - 02:14 AM.

[ravetrooper]

This is a great question, one I've been considering myself for a while now. I don't have an answer yet but I thought it would be good to give this thread an extra bump

[SirBrass]

I went ahead & desoldered the connection and wrapped the braking lead in heat shrink. I'll put up with the wind down till this can be explored better.

But visible arcing on the brushes through metal end caps is no bueno. Need to figure out how to electrically do a gradual brake.

I think the key will be to present a balanced load to the motors (which are now circuit-wise) acting as a current & voltage source.

[Draconis]

What.  How do you have this circuit set up?  From the way you phrase it, you make it sound as though you are switching the motors to either reverse current supply, or lower current to gradually slow them down?  That's not what you need to do.  When the current is switch off, the motor stops being a load on the power supply, and essentially becomes a charged inductor.  Because that inductor is supplying power to the circuit, you just need to drain it through a resistor.  The easiest way to do that is with a SPDT microswitch that has the normally closed half wired to a resistor, then to the positive poles of the motors.  Of course, this is assuming that you are wiring your system so that the positive pole of the battery is hardwired to the motors.

[SirBrass]

What.  How do you have this circuit set up?  From the way you phrase it, you make it sound as though you are switching the motors to either reverse current supply, or lower current to gradually slow them down?  That's not what you need to do.  When the current is switch off, the motor stops being a load on the power supply, and essentially becomes a charged inductor.  Because that inductor is supplying power to the circuit, you just need to drain it through a resistor.  The easiest way to do that is with a SPDT microswitch that has the normally closed half wired to a resistor, then to the positive poles of the motors.  Of course, this is assuming that you are wiring your system so that the positive pole of the battery is hardwired to the motors.

I have motor loom positive run to switch COM, switch NO is wired to battery +ve, motor loom negative is wired to battery -ve, and braking short is spliced between battery -ve & motor and wired to switch NC.

So, what resistance should I run? 10k? And power rating?

Edited by SirBrass, 03 March 2017 - 02:03 PM.

[Draconis]

So, what resistance should I run? 10k? And power rating?

 

That would depend on the motors you are using, the stall current draw, the mass of the flywheels, and how quickly you want the flywheels to slow down. 10K 1/2W or better should be more than enough.

[SirBrass]

I'm running Blade 180s in the stryfe on 2s (60c 2200mah. It's what was supposed to go into the RS which is in major revision/disassembly and will soon be on 3s). I'll be getting a smaller 2s soon that won't be so cramped even with a 20mm extended battery tray.

I'll get one of those resistors at RadioShack on my way home today.

[shardbearer]

A 10k resistor is way too high a value, and won't actually brake your motors a noticeable amount. You probably want something in to 10 Ohm order of magnitude. I believe an inductor could also help.

Edited by shardbearer, 07 March 2017 - 10:26 PM.

[SirBrass]

A 10k resistor is way too high a value, and won't actually brake your motors a noticeable amount. You probably want something in to 10 Ohm order of magnitude. I believe an inductor could also help.

Yup, found that out the hard way though I should have known as I can do ohms law in my head easily enough.

However, it's no big deal. I didn't even notice the lack of braking during Saturday's war. Also, having the ability for the flywheels to eject any trailing darts if the pusher doesn't brake fast enough if I put a full auto kit in this will be nice. Jammed darts due to pusher makes for me being an easy target as I figure out that something went wrong and then try to transition to pistol while running to get behind the nearest cover & hope I don't get bunkered.

BTW, the 180 stryfe was awesome. With worker wheels, red cage, ekind waffleheads, and blade 180s on a high C 2s lipo, this thing was shooting darts laser straight & very fast.

[meow121325]

I am making a deploy with a demolisher integration making it run on flywheels and it runs on a drone limo but I need help with the shell and how to join them