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Thread: Bad experience with Max Mobility Smart Drive

  1. #31
    Quote Originally Posted by nonoise View Post
    ...the voltage varies from 0 to 5 v.
    That's exactly what the RC time constant is for - to delay the time it takes to ramp up from 0 to 5V. Go to 2:20 where he demonstrates this delay. He explains that one of the ICs on the board is a digital potentiometer. The potentiometer is adjusted to select the desired delay. Of course, there's more to the circuitry. But this is the part that addresses your concern - " they ramp up to wide open too fast, so flipping is a concern."

  2. #32
    Quote Originally Posted by August West View Post
    When you rewire the control circuitry and specify MOSFETs (vs just referring to them as transistors), that tells me that you have a pretty good understanding of electronics. A schematic would be necessary to take it to the next level of troubleshooting. However, if it is a component/quality issue rather than a design issue, then a schematic may not get us anywhere.
    Electronics is a hobby I enjoy but do not understand very well. That said, my previous comment spoke about what I thought about the MOSFETs. It was out of curiosity that I wanted to remount the PC board on better "springs" to see if it made a difference in how the accelerometer responded. I just haven't done it yet.
    I have had periodic paralysis all my life. I lost my ability to walk in 2011 beginning with a spinal block, which was used for a hip fracture caused by periodic paralysis.

  3. #33
    Quote Originally Posted by August West View Post
    That's exactly what the RC time constant is for - to delay the time it takes to ramp up from 0 to 5V. Go to 2:20 where he demonstrates this delay. He explains that one of the ICs on the board is a digital potentiometer. The potentiometer is adjusted to select the desired delay. Of course, there's more to the circuitry. But this is the part that addresses your concern - " they ramp up to wide open too fast, so flipping is a concern."
    How would I pick out what resistor and condenser to use?
    Edit: The answer, or most of it seems to be here: https://www.electronics-tutorials.ws/rc/rc_1.html
    Last edited by nonoise; 08-12-2018 at 06:51 PM.
    I have had periodic paralysis all my life. I lost my ability to walk in 2011 beginning with a spinal block, which was used for a hip fracture caused by periodic paralysis.

  4. #34
    Quote Originally Posted by nonoise View Post
    How would I pick out what resistor and condenser to use?
    Edit: The answer, or most of it seems to be here: https://www.electronics-tutorials.ws/rc/rc_1.html
    Correct, you used fixed R and C to select 5 tau as your reference to start. Then you use a potentiometer in series with the fixed resistor to trim R empirically. I would start on the low side for R value. Because you can always add resistance with the potentiomter but you can't subtract it.

  5. #35
    One thing to keep in mind is that you want to dampen the acceleration profile only. You (probably) don't want to damp the deceleration profile in order to use to inherent dynamic braking properties of the motor to stop quickly. That means you have to somehow enable the RC delay when going from 0 to 5V and bypass it when going from 5V to 0. But the desired delay is probably about a half second delay so it not matter if you slow down half a second slower.
    Last edited by August West; 08-12-2018 at 07:40 PM.

  6. #36
    Quote Originally Posted by August West View Post
    One thing to keep in mind is that you want to dampen the acceleration profile only. You (probably) don't want to damp the deceleration profile in order to use to inherent dynamic braking properties of the motor to stop quickly. That means you have to somehow enable the RC delay when going from 0 to 5V and bypass it when going from 5V to 0. But the desired delay is probably about a half second delay so it not matter if you slow down half a second slower.
    I'll respond to this one first because I think I understand it. Hub motors don't have the inherent braking properties that brushed fixed magnet motors do. But these are geared brushless hub motors so there is some mechanical (not much) braking. As for going from 5v to 0v I was assuming the motor would eat the excess up nearly instantly.
    I have had periodic paralysis all my life. I lost my ability to walk in 2011 beginning with a spinal block, which was used for a hip fracture caused by periodic paralysis.

  7. #37
    Quote Originally Posted by nonoise View Post
    Hub motors don't have the inherent braking properties that brushed fixed magnet motors do.
    I'm glad you know that. I'm not really up on hub motors. The delay circuit is actually electronics 101, a very basic thing. The bigger challenge is integrating the circuit into the existing control circuit. That can get tricky. But you said that you already attached a hardwired throttle, so I guess you have that part under control. How did you know where/how to connect the hardwired throttle?

  8. #38
    Quote Originally Posted by August West View Post
    I'm glad you know that. I'm not really up on hub motors. The delay circuit is actually electronics 101, a very basic thing. The bigger challenge is integrating the circuit into the existing control circuit. That can get tricky. But you said that you already attached a hardwired throttle, so I guess you have that part under control. How did you know where/how to connect the hardwired throttle?
    It's just e-bike stuff. After paying someone to connect the pieces together for my recumbent I decided anyone can do it. The main part is the controller with bunches of premarked wires coming out the end. They are marked for battery, motor, brake, (regen, not geared motors) throttle, and ignition, usb, I think that is all. Obviously not all are used. I used Endless Sphere forum for guidance when lost since some of these makers are not standardized.

    So what I am getting now is that of the three wires for the throttle I would use the negative and the signal wire breaking the signal between the throttle and the controller with the resistor closest in line to the throttle?

    edit, last word to throttle
    Last edited by nonoise; 08-12-2018 at 10:22 PM.
    I have had periodic paralysis all my life. I lost my ability to walk in 2011 beginning with a spinal block, which was used for a hip fracture caused by periodic paralysis.

  9. #39
    Quote Originally Posted by August West View Post
    Correct, you used fixed R and C to select 5 tau as your reference to start. Then you use a potentiometer in series with the fixed resistor to trim R empirically. I would start on the low side for R value. Because you can always add resistance with the potentiomter but you can't subtract it.
    They show a 5v example with this result T = R x C = 47k x 1000uF = 47 sec. Obviously too long, but wouldn't 1k give 4.7 sec? That is way slower than now. I could just buy a few resistors and a cap and try some. But what res wattage 1/2 okay? The wires are like 22 gauge.
    I have had periodic paralysis all my life. I lost my ability to walk in 2011 beginning with a spinal block, which was used for a hip fracture caused by periodic paralysis.

  10. #40
    Quote Originally Posted by nonoise View Post
    They show a 5v example with this result T = R x C = 47k x 1000uF = 47 sec. Obviously too long, but wouldn't 1k give 4.7 sec? That is way slower than now. I could just buy a few resistors and a cap and try some. But what res wattage 1/2 okay? The wires are like 22 gauge.
    The delay is approximately 5RC. I would reduce the capacitor value. 1000uF is very large physically. How about 47K and 1uF for a delay of about 235 milli seconds to start? That's a long time in electronics. Then increase R value empirically. The resistor power rating can be very small. Full power = V^2/R = 25V/47K = half a milliwatt.
    Last edited by August West; 08-13-2018 at 12:06 AM.

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