Let's Make Robots!

'Flopping fish'

First of all I'm art student, therefore (as you may expect) I know nothing where electronics is
concerned. I have come onto here wondering if you could guide/ recommend/ give any advice.

I'm currently starting a new art project as part of my university course.
What I require is a series mechanism/ piece of electronics which could fit inside a
model of a fish (hand size) and make it flop without assistance.

I am very interested in the things you guys come up but unfortunately for my project I have little time to learn. I would (if anyone is interested) pay a very helpful person to possibly come up with something for me?

possible something constructed like this?


very much appreciated :)


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If you are willing to pay for it, and want something like what Crapfu made, I think you can just go to him, as far as I am concerned, he makes / try to make a living out of he's cool creations: crapfu.com

jaja crabfu not crapfu jajaja....

As alway those works from crabfu are inspirational... one of this days I will try the tortoise... its so cool..!!

Question time:

• What's your budget?
• How many fish, just one?
• Is there a certain material you want to use for the skin/outer body?
• Do you want it radio controlled like Crabfu's fish, or totally autonomous?
• How long does the fish need to be able to flop around for on a fresh set of batteries?

I have sent an email to him but Im waiting a reply.


Answer time:

  • My budgets pretty flexible.
  • Just the one fish yep :)
  • The skin/ outer body I was planning on making and putting on myself (slip it over the working parts like a sock?) - I intend to make the skin using a mix of plastic fishing lures.
  • I would rather it be autonomous (unlike crabfu's)
  • I would ideally want the fish to flop constantly. It would be in one spot for 3-5 days. I was thinking of making a raised floor especially for it to rest on- this would hide the power supply.

Hope that answers your questions?

Oh one more thing, and possibley the biggest problem. It needs to be ready in 4 weeks.

Hmm, 4 weeks is possible, if you source everything as locally as is reasonable. Fortunately there are plenty of Brits who like their RC toys, so finding the parts quickly should be easy enough.
Normally I'd suggest making use of the wonderfully talented people here at LMR, but time is not on your side, and I think you'll be better off having an imperfect solution in your hands very soon (which you can then improve upon), compared to waiting a few weeks for a hopefully perfect solution.

To that end, I think the most suitable option is to go for a pre-made servo controller (possibly a 'servo tester') that can control one or two servos inside the fish automatically. No programming, no soldering, it'll cost you a bit more than a custom solution might but if something goes wrong you can pick up replacement parts quickly.
I'll have a look at some UK suppliers and see if I can make a more specific recommendation.

Will this 'fish' be exposed to water at all? Shallow puddle, incidental rain, anything like that? Power supply will be easy enough, one of those little wall adaptors spitting out 5V or so will be perfect, and cheap too.

Ah I see. I'll look a little closer to home in that case. It just seems a little harder to find those with the know-how here in england. It might help if I get familiar with basics too.

Initially I wanted it exposed to a puddle yes, but it's not so important now.

Thanks for your response telefox, very helpful of you :)

I had a bit of a poke around the interwebs - take a look at these two servo testers:
G.T. Power Servo Tester - can be bought from here among other places.
Esky Servo Tester EK2-0939 - possible sources include this seller.

The important things about these two controllers are that they can be run in auto mode, sweeping any connected servos back and forth continuously, and secondly they're cheap =)
They can also be powered from an external source easily enough, and both can control more than one servo at the same time. The Esky servo tester is quite big compared to the G.T., but it may be better to keep the servo tester inside the platform in any case, and just run the servo wires up into the fish. Also the Esky has the nice advantage of being able to adjust the auto-mode sweep rate, I think the G.T. just sweeps at a preset rate. If you waterproof the platform and only have the servo/s inside the fish it actually wouldn't be that hard to waterproof the whole thing.

As for choice of servo, well, there are too many options. Servos come in all ranges of sizes and powers, but virtually all servos will work flawlessly with these testers. Maybe you should start with a really cheap one of a sensible size, and if it's not fast/powerful enough go up to a higher quality model.

Ah I see, I see. I might get some parts (those suggested) and play around.

The offer is still open though? if somebody is up for making a setup of around 4 moving joints? which I can place inside a plastic cover. And make the fish wiggle in a pattern of somekind.... I'd cough up the money to make it happen?

Any idea how much room there would be inside said cover? 4 joints is actually quite a lot for a fish, where do you want the points of articulation?

it would be about 7-8 inches long ( head to tail)

I want the movement to be like quick spasms,

spasms as in; a quick burst of energy

I would like these to  occur in a slightly spontaneous patern ;3 second pause, one happens, 2 second pause, one happens,1 second pause, one happens , 5 seconds pause, one happens, 4 second pause, one happens etc etc. I basically want them to build up and then build down/ relax - in a looping pattern. Failing this a standard pattern would be fine. If it could be changed so the spasms last varying times that too would be great.

I want the spasms to happen like a quick mexican wave ( the movement to run from the head to the tail quickly)

http://www.youtube.com/watch?v=AZzg5AgxSNE - um sort of like that? but not so aggressive,

 ANOTHER IDEA ( probably better?)

I was thinking when the fish first come out of the water and flop they put alot of energy into it and end up jumping (below clip). If I had the workings/ mechanism inside which do the mexican wave motion, I could make the fish jump by placing it on a vibrating platform/ board. I would make this platform myself using woofers/ speakers to create the vibrations. By doing this I myself can set the intervals of these flops/ spasms?