Let's Make Robots!

What would you call a "Wiper"

I have searching mouser for 1/2 hour now and for the life of me, I can not figure out what to call one of these things. "Wiper" gets me nowhere. I am looking for a small copper contact, sorta springy, that would ride along an exposed trace on a PCB. Specifically, I am trying to transfer power through a rotating joint. This would involve 6 concentric rings etched on a pcb with a 6-pronged "wiper" on the rotating part above.

What is the fancy name for these things?

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Rotary contacts, (slip rings), are also found in phone cord untanglers.

These are in plentiful supply at "dollar stores" here in the states. If you need more than 4 circuits, stack'em.

Have you tried the term rotary union?  These are like slip rings but are not only electrical but also hydraulic and pneumatic.

Mo--om, Phineas and Ferb are making a rotary union!

Hey thanks, one more thing for me to google. Awesome.

Hey I almost forgot about this guys solution to this problem.  If you want to program a PicAxe or something through a rotatry contection try a stereo plug.  Here's the link.  This was posted in July of this year.



Ok, more info and I guess I will just come out with it...

Think of an excavator and the pivot between the tracks assembly and the cab/arm. Battery pack and motors are on the bottom, brains etc are in the cab. I will be transferring motor-level power as well as raw battery power through this guy. Mind you, we are talking about some pretty small motors here, and little current on the data side --maybe a total of 1 amp going through any one contact at any time. Total dia would be around 5cm or so. I should add that, while I appreciate the suggestions of those AWESOME pre-made rotating joints, I am actually just looking for the "fingers" themselves. The link that basile gives is exactly what the disc will look like, with the exception that I will probably etch my own rings. 

You got a good one there, oddbot --I have thought of many ways of trying to use the laser cutter to get this done --Alas, it is just not going to get through metal (even really thin stuff). I can however, coat the copper with a mask and then use the laser to burn off the mask where I want etching to occur. The only issue here is that I have never actually tried to etch all the way through a peice of copper --Well, I have, but not intentionally --only when I forgot the board I was etching and left it in too long!

Thank you for the link to that arm, mint --It is not only beautiful, but it looks like he may have made exactly what I want to do --I will shoot him an email.

I appreciate all your help on this, guys --I just woke up, found all the responses and need to start checking all your links again to see if their paths will lead me to where I need to be.



Since your a tradesman like myself I'm sure you know about the replaceable brushes you can get for power tools. I suspect Walter has them in his drill motors.

They would be your best option for power transfer and maybe for data as well if you can get them small enough. Any data you are going to transmit through the brushes will be noisy so it is best to use relatively low frequencies with good noise filtering.

The schematic below is an example of how you might set it up. I didn't know how to draw slip rings so the yellow boxes are where your wipers/brushes meet your sliprings. Because of the noisy connection I suggest an extra large capacitor on your regulator input. In this example I have shown 1000uF. This should ensure good power flow to the regulator.

I have shown 4 data lines which I assume would be PWM and direction signals for a motor controller. The filtering I have shown should be good enough to prevent the motors reversing everytime there is a bit of noise on the line without interfering with the PWM signals. Some experimentation may be required with the resistor value.

You know, you said it once before, but I didn't pick up on it. Brushes from power tools! It clicked this time. Brushes are the most perfect answer in the world! They are rectangular and thus a little "track" for them will be easy to make. They already have little wires attached... Awesome!! That is genius. I already had the rings figured out (how to lay them out and etch them) but it was those darn contacts... That wife of your's is a lucky gal, I tell ya!

Thanks bunches for the schematic. I assumed as much in terms of the huge cap but I would have over looked the smaller ones on each of the motor controller lines. 

Oh! This one I got cookin' up is going to be a good one!

Anytime my friend.

I think you will also find that those brushes tend to have some graphite or oil in them for lubrication. This should help prolong the life of your sliprings.

As I always understood, the motor brushes were made of graphite. At least in my local lingo they're "koolborstels".

Carbon brushes.