DC motor control

Hi All,

I’m completely new the the world of arduino so I thought I would dive in with a project.

I have a antique metal prosthetic hand that I have restored to a partial working order but I thought it would be cool to bring it up to date and add some control to it, eventually using the myo sensors. I did a little investigation and purchased an arduino starter kit to get going.

I should add that its not possible to alter the hand (I cant add more switches and so on) its quite valuable so cant be atered.

long story short the pictures will make much more sense.

I have a 12 DC motor and 1 microswitch to run the hand and its grip… the main brass wheel can only turn for about 180 degrees, any more and it will destroy the mechanism.

I thought I could use the microswitch to initialise the hand or create a start point that I could then run the motor for a set time to close the hand. then use and external switch to open the hand back to the microswitch start point and so on.

there are other options to add 2 switches to the 2 of the fingers but that can come later. once I have some idea of what im doing. to be honest im a bit overwhelmed with it thus far.

if anyone can point me in the right direction that would be great.

cheers in advance

Use a different motor with a built in shaft position encoder.

It seems that you have already altered the hand, so why aren't additional alterations allowed?

that's the thing. :o

I haven't altered the hand at all. its all original. all I have done is restore/repair it. initially the motor wasn't working and the mechanical joints had been forced/broken.

Its the original switch, motor and so on... even the original micro switches in the fingers are there although i still need to repair these but could be included later.

As you say it would be easier to use a stepper or something with an encoder but its not really an option.

I can supply more images if this would help.

Would it be possible to mount a LED/phototransistor pair to sense (count) the gaps in the gear teeth as it turns? You could use double sided tape to avoid drilling the hand.

Or, small magnets mounted (RTV?) to a moving part and sensed by a hall switch mounted to a non-moving part.

.02

Thanks for the reply,

Thats something I considered dougp:)

the gear teeth are quite small so i kind of ruled that one out a few days back.

the magnets is something I considered with reed switched but haven't considered them much further. the large brass gear has a range of rotation of about 180 degrees. I had thought of using the microswitch as the reference point and basing everything off from that point.

i was thinking along the lines of when the switch is active then I could move the motor forward for a specific time (or time it takes to close the hand). once that point is reached I could then reverse the motor back to the microswitch. (would put in more control switches later for the open close function)

its not going to be used as a functioning hand and its more for display as well as learning some arduino programming along the way.

cheers in advance :slight_smile: