need help with robot DCmotor for show

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andyfromdenver

Well-known member
Joined
Nov 13, 2012
Messages
359
Location
Athens, GA
Hi beautiful people :)

concept:
to cut down on personnel for upcoming shows, i want to park a robot infront of a piano and have him sway back and forth and have the arms move. then I can use a prerecorded kybd track and it will sort of “look like” the robot is playing.

the robot is R.A.D. 2.0. a late 90s toy.
the arms move using  a 6VDC motor and gears.

problem:
I need a circuit that will operate the motor in one direction for 1-2sec then reverse direction for 1-2sec

I have surmised that one route is using a dpdt relay to switch the pos and neg to the robot, but how do I add a timer circuit to this?

space inside is limited.
my plan is to have a push switch that i can step on to activate the entire circuit.
push once: arms begin to swing open and close
push again: arms stop

can anyone please help me?

i’ll be reading, but could use some guidance.
I am not sure if a microprocessor is the right route, because of the need to power it off and on quickly.

additionally, anyone with insight into how to dampen the noise from these plastic gears or the motion in general?

thank you!!!

this will be so cool eventually.
I am going to add some blinky light stuff or maybe a sound activated light situation for the eyes.

I plan to have the robot sway to and fro by maybe hacking apart an oscillating room fan and repurposing.

Andy
 

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Hi Andy,
I have no expertise in these things at all Im afraid , There is however another contributor here who goes by the name Sahib ,I think he knows lots about robotics , Im certain he'd have the solution to your question .
Best of luck with the show ,
 
Those Engineers Notebooks have been cheap when I've found them at hamfests and such, but there's an even better deal, they're free and easy to find online:
https://archive.org/search.php?query=forrest%20mims
 
80hinhiding said:
Ahaha that's funny man

I wasn't sure if you were kidding first, but it could be kind of cute/funny/entertaining.

My thought is about a sidechain.  Use that as a trigger to move it to the beat of the music, is that possible?

Adam

Hi Adam, sorry I missed your question/ idea.  That would be cool, but the movement is not that fast, i'm afraid.  What I do plan to do is a simple sound to light circuit (already have a Velleman kit) so at least the eyes will light up to the music.

Maybe if I ever meet some amazing young power nerds and I can excite them to help me in real life, we'll do a fancier version :)

Andy
 
I figured it out on the fourth try.
needed astable mode and an npn transistor.
scheme in next post
 

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would someone be so kind as to critique my schematic?
It’s all working and I just want to probe for inefficiencies/superfluous-ities/improvements. Sorry for the bad dpdt 5VDC relay drawing. it flips the pos&neg.
If I have the 39k resistors perfectly matched, the alternating motor length should be identical, but the arms are drifiting open over time so the times aren’t 100% perfect, or the gear mechanism is not perfect, i dunno.

Thanks!

*edit in, i found out the smoke-y way that using a smps pcb +12 and +5 sharing ground is not correct, lol. I’m strategizing the power supply now. I’ve left this on for a while and it is operating nicely, so it seems my scheme is ok, if not perfect*

 

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I do not think you will achieve anything better than using 1% resistors. 555 will drift but you have bigger worries.

Gear trains will be reasonably well matched. The motor mismatch is also not so significant. But the loading between the two arms are probably significantly different. So, I suggest you build two astables to drive both arms separately and tweak them to synch as best as you can (by playing with the charge/discharge time constant).
 
sahib said:
I do not think you will achieve anything better than using 1% resistors. 555 will drift but you have bigger worries.

Gear trains will be reasonably well matched. The motor mismatch is also not so significant. But the loading between the two arms are probably significantly different. So, I suggest you build two astables to drive both arms separately and tweak them to synch as best as you can (by playing with the charge/discharge time constant).
Thank you for writing, I appreciate your input! :)
I am thinking about your suggestion and what can be done. Perhaps shortening the switch time and making the duty cycle variable will permit me to use the single motor. I am hoping I can set it in a good spot and get 30 minutes of show time out of this situation  ;D :eek:
I already want to work on version 2.0 maybe with lego mindstorm and bulking up the visual physically with more legos.

tbc,
Andy

 
Ok. drift problem is solved. separate power supplies from fleamarket obtained.
There are no other issues and i’ll execute this and hopefully upload a vid.
I may add another up and down movement, which should be really simple.
Drift address: I simply added a rheostat in series with one of the timing resistors (5K pot).
The pot has a tight turn and i’ll add it on the robots back with a knob and marking for ideal setting and any correction needed.

The head has cool blue leds thru the red plastic eyes, which looks really good.
the mouth has a simple sound to light multi colored display which works nicely.

Next step is to move it to a protoboard and solder it in. I am socketing the relay and 555. Then plastic surgery to install it  :eek:

Then I can move on with my life!  ;D
j/k

 

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