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Wired Remote Control Without Batteries

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This Dynamo Rover is a wired remote control toy that does not require any batteries, but uses the renewable energy source of kids’ muscle power (or the muscle power of adults addressing their inner child).

The idea of using a dynamo or generator to power a toy can be found in products like 4M’s Dynamo Robot. What I did is adding a basic mechanism for steering control and working out a simple way to build the complete rover out of two hacked servos, three wheels and just a few extra parts.

This little project demonstrates how a hacked servo with a crank becomes a pocket-sized generator. As servos are based on a DC motor, simply reversing the direction in which you rotate the crank reverses polarity and gives you forwards and backwards movement on the rover.

Inspired by toys from the times that remote control largely relied on mechanical solutions, I made the backwards movement into a steering action. By making one wheel run forwards only and cleverly positioning the other wheels, you can still go straight forwards, but moving backwards becomes turning, almost on the spot. This way you can get anywhere you want (al be it not in the fastest way).

Here's a video of the Dynamo Rover in action:

The very basic mechanism is based on the use of a spoked wheel and a simple “catch” with tape as a hinge. Here is a video in close-up:

If you can pick up two cheap servos, the cost of this project is pretty low. The wheels and the few extra parts shouldn’t set you back more than couple EUR/USD.

I'm planning on making a version with laser cut chassis, wheels and "catch", somewhat more expensive, but even simpler to assemble. I'm thinking of giving it a scorpion look, with the tail holding up the wire and the front wheels integrated in the fangs.

If you like this Ible, please give it your vote.
 
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Ugifer1 year ago
Great idea!

Did you know it had made the Makezine blog?

http://blog.makezine.com/page/2/

Nice way to demonstrate energy conversion and also the inefficiencies in those conversions - I bet it takes quite a bit of cranking to get the 'bot to go one turn forward. Could lead easily to a discussion of conservation of energy etc. As well as just being fun!
masynmachien (author)  Ugifer1 year ago
Thanks!

It takes about two turns of the crank to make the powered wheel make one turn.

That is playable, but does indeed clearly show the influence of conversion in efficiencies.

Of course a true comparison and determination of the efficiency would mean measuring the torque. The torque manually applied on the dynamo servo is not high, but clearly higher than needed to push forward the rover.

Actually an efficiency of 50% is the maximum with the nominal efficiency of the little DC motor in each servo probably in the range of 70% (and 70% x 70% = 49%).

What is interesting to see is that when you try and speed up the crank, the resistance drops and the rover slows down. In that case you make the motor of the dynamo servo turn faster than the rpm range where it works well.

What is also interesting to see is that when I add a LED in parallel to the motors it obviously lights up when cranking in one direction, but also lights up faintly when cranking in the opposite direction. When I power the LED with the dynamo servo, without the second hacked servo attached, the LED only lights up when turning the crank in one direction. So it is the combination of the two motors that causes spikes with reversed polarity.

I was also thinking of using a stepper motor as generator. The electrical efficiency of a stepper motor isn’t very good either, in particular at high rpm. But we’re talking about low rpm’s here and the mechanical efficiency is much better as you can drop the gears. But then of course the output needs rectifying to power a DC motor, which looses the simple reversing function. Obviously one can always add a reversing switch. Actually, I’m wondering what connecting a stepper motor to a stepper motor would give. Will one “follow” the other step by step as long as the load is low?
masynmachien (author)  masynmachien1 year ago
Update: after not finding any info on connecting a stepper motor to another stepper motor, I picked up two bipolar stepper motors and tested if one can drive the other by connecting them directly: it does not work. No movement in the second stepper motor at all.
randofo1 year ago
Clever! I like this one a lot.
masynmachien (author)  randofo1 year ago
Thanks!
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