[sudo-discuss] wheelchair motor controller
Robert Benson
sf99er at gmail.com
Thu Jul 16 09:04:37 PDT 2015
aha. thank you for the invaluable lesson on resistance.
the relationship between volt/ohm=amp has escaped me until not.
in ohm's law: v=i*r, the i often confuses me.
maybe only one controller per motor will be suitable but ultimately we will
want to drive it with dmx(arduino), me thinks
oh, the brake's 100ohm(5w) resistor got hot fast when the wheel started
spinning. the motor's resistor did not.
On Thu, Jul 16, 2015 at 1:51 AM, Jake <jake at spaz.org> wrote:
> if you put a 1 ohm resistance, you will just blow up the resistor.
>
> 24 volts divided by 1 ohm = 24 amps
> 24 volts times 24 amps = 576 watts
>
> you need to find the highest number of ohms that will still cause the
> motor controller to not give you an error. Lets say you find that a 100
> ohm resistor (in place of the missing motor) causes the controller to be
> OK. When you move the joystick, and it tries to turn the fake motor, it
> will give it up to 24volts. But it's a 100 ohm resistor.
>
> 24v / 100 ohm = 0.24 amps
> 24v * 0.25 amps = 5.76 watts
>
> if it works with a 100 ohm, you should use that. 5.76 watts is
> reasonable. 576 watts is most of a horsepower and is not reasonable.
> 5
> in case you're not confused i'll tell you this: the power a motor
> consumes (from a fixed voltage source for example) depends on the amount of
> force it's putting out.
>
> So if you have a motor just spinning a wheel in the air it doesn't take as
> much power as if you're making it grind grain, or push a fat person up a
> steep incline. The ohms you measure when you use a multimeter on the
> stopped motor correspond to its MAXIMUM power, basically.
>
> so if you stopped the motor and applied 24v, 576 watts would flow through
> it and heat it up pretty fast. But if you let it spin freely in the air,
> its effective impedance would be much higher than 1 ohm!
>
> as for how to isolate the motors for different jobs.. we can read the
> manual on the control box and adjust the settings, or just hook up the
> computer control and let it do all the work. I don't know though.
>
> -jake
>
>
> On Thu, 16 Jul 2015, Robert Benson wrote:
>
> i'm such an idiot. when i checked the motor resistance, i checked the
>> controller's motor circuit resistance. the actual motor resistance is 1 ohm.
>>
>> however, even idiots get lucky...the motor worked with 100ohm. having
>> realized the above, i will not power it again until i find a 1ohm resistor.
>>
>> for the record, moving the joystick in any direction moves the wheel in
>> some way. so how do we isolate the motors for different jobs?
>>
>> On Thu, Jul 16, 2015 at 12:49 AM, Jake <jake at spaz.org> wrote:
>> what do you mean both motors
>>
>> you only have one motor last i checked.
>>
>> On Thu, 16 Jul 2015, Robert Benson wrote:
>>
>> my ohmmeter had a "k" in front of the ohm symbol when it read
>> 150 k ; not a M or just the ohm symbol.
>>
>> datasheet i posted earlier seemed to suggest the motor is
>> 120V while the brake solenoid is 24V
>>
>> both motors read 150kiloohm :/
>>
>> On Wed, Jul 15, 2015 at 11:45 PM, Robert Benson <
>> sf99er at gmail.com> wrote:
>> gonna have to have a high wattage rating, huh?
>>
>> On Wed, Jul 15, 2015 at 11:41 PM, Robert Benson <
>> sf99er at gmail.com> wrote:
>> 150k says the motor
>>
>>
>> on hunt for same
>>
>> On Wed, Jul 15, 2015 at 11:30 PM, Jake <jake at spaz.org> wrote:
>> a wire jumper is approximately zero ohms, which will
>> destroy stuff when power flows through it.
>>
>> the motor controller is complaining because it sees
>> infinity ohms across the missing motor's terminals. So just like the
>> brake, the
>> solution is to put a resistor across the missing
>> motor's terminals.
>>
>> if we want more than one motor, we can just put the
>> other motor on the missing connector and use the one controller to control
>> both
>> motors.
>>
>> if we need more than two motors, we can use relays or
>> switches with the same controller, or we could get more controllers. But
>> lets
>> start
>> with one or two motors.
>>
>> -jake
>>
>> On Wed, 15 Jul 2015, Robert Benson wrote:
>>
>> agreed
>>
>> i was thinking that since controller still said
>> check right motor connector after i crossed the brake terminals w/resistor
>> that
>> i needed to jump it. when i jumped
>> them the check right motor code went out which
>> seemed to indicate the error was corrected. luckily i had to hold the jump
>> wire &
>> resistors against the contacts so i
>> noticed the heat immediately after touching the
>> joystick and cut the power. check right brake code has returned as before.
>>
>> maybe building a 120vac/24vdc controller would be
>> better...we probably want four or more of these puppies for the lighting
>> trusses
>>
>> On Wed, Jul 15, 2015 at 11:00 PM, Jake <
>> jake at spaz.org> wrote:
>> you should not short out stuff with even a
>> thin wire.
>>
>> you are going to destroy the motor
>> controller if you continue on this path
>>
>> what are you thinking? do not short out
>> the motor terminals.
>>
>> On Wed, 15 Jul 2015, Robert Benson wrote:
>>
>> connected a thin wire across motor
>> side of connector (while 110ohm across brake side) and got movement but
>> wire got
>> real hot...too scared
>> i'll damage the controller
>> right now to try a bigger gauge
>>
>> On Wed, Jul 15, 2015 at 10:26 PM,
>> Robert Benson <sf99er at gmail.com> wrote:
>> connected 110ohm across brake
>> terminals but no worky
>>
>> On Wed, Jul 15, 2015 at 9:44 PM, Jake
>> <jake at spaz.org> wrote:
>> should be fine
>>
>> On Wed, 15 Jul 2015, Robert
>> Benson wrote:
>>
>> might have to upgrade the
>> roomba motor & controller to hit mice
>>
>> will 150ohms be too
>> much/work/hurt anything? i found a 100ohm 5w & 50ohm ?w i plan on running
>> in series
>> if i dont find a more
>> suitable value
>>
>>
>> On Wed, Jul 15, 2015 at
>> 8:21 PM, Patrik D'haeseleer <patrikd at gmail.com> wrote:
>>
>> On Jul 15, 2015
>> 6:05 PM, "Jake" <jake at spaz.org> wrote:
>>
>>
>> if you want
>> to play with robots i have plenty, like roombas which won't break
>> your legs
>> running you over.
>>
>>
>> Roomba + tazer = no more
>> mouse problems!
>>
>> Patrik
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
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