Making a small circuit with a moving arm?

Thread Starter

axisus

Joined Dec 18, 2019
3
Apologies if this is not the right forum to be asking questions like this .....

OK, so I know nothing about circuits/electronics at all, well, I did make a guitar neck where a light goes on when you use the frets, but I was seriously winging it! (It's a cool guitar though!)

Anyway, I find myself wanting to make a small battery powered circuit and I have no clue how to go about it. I want a small lever that at a press of a switch moves 180˚ or so quite quickly, and then when the contact is lost it flips back again.

Is this something that anyone could help with? If so I can explain why I want it (it's a cute idea!). If not then I shall go back and hide under my rock! Thanks.
 

TeeKay6

Joined Apr 20, 2019
572
Apologies if this is not the right forum to be asking questions like this .....

OK, so I know nothing about circuits/electronics at all, well, I did make a guitar neck where a light goes on when you use the frets, but I was seriously winging it! (It's a cool guitar though!)

Anyway, I find myself wanting to make a small battery powered circuit and I have no clue how to go about it. I want a small lever that at a press of a switch moves 180˚ or so quite quickly, and then when the contact is lost it flips back again.

Is this something that anyone could help with? If so I can explain why I want it (it's a cute idea!). If not then I shall go back and hide under my rock! Thanks.
How small is small? How fast is fast? What does the lever do? 180°±1° or 180°±30°? Required torque at what radius? More detail will get better responses.
 

Bernard

Joined Aug 7, 2008
5,397
Wire a small motor as a linear actuator with 0 deg. & 180 deg. limit switches. Start is with DPDT push button switch. Push & hold, motor advances 180 deg. , hits limit SW & stops Button released, motor reverses & at 0 deg. limit SW stops motor.


































7
 

Thread Starter

axisus

Joined Dec 18, 2019
3
Thanks for the replies all. Just to explain a bit more: As I mentioned before I like to build electric guitars in my spare time. I am just starting to make a very 'rustic' telecaster, and I am using a worn old piece of fence as the front of the body. It occurred to me that it would be amusing to have a hole on the front, and then when I play a certain fret high up the neck it would connect power so that a wee mouse would suddenly 'pop up' in the hole, and disappear when I was no longer playing the fret. So, the speed is arbitrary other than 'mouse speed' (eg not too slow). The 180˚ is arbitrary - I just want to move the mouse completely out of sight. Torque - no idea but I will make a very light mouse model. The size needs to fit in a guitar body so depth of 40mm max.
 

AlbertHall

Joined Jun 4, 2014
9,310
From the comparison table I linked I linked, Even the smallest should do that job. 180 degress in about 200ms and would move 1oz 4 inches.
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Bernard

Joined Aug 7, 2008
5,397
A small RC servo would work but a small DC gearhead motor will also work with simpler electronics. Just as an example, from All Electronics, USA, CAT # DCM, Model GA12-N20, 180 deg. in .3 sec. 3-12V, 1:10, 2kg cm @ 12V
15 X 12 X 10 mm. additional: 5 V relay, DPDT, 2 SPST NC SWs. , 2 diodes, & SP.ST fret SW
 
Last edited:

Bernard

Joined Aug 7, 2008
5,397
I think that this will do it. With Fret SW open motor M will run in reverse
until arm or cam opens SW B, mouse gone & all power off; with F SW closed, relay, RY, reverses polarity to motor which then runs until mouse is out & SW A opens stopping motor, releasing F SW starts mouse retreat. Diodes general purpose 1A like 1N4001 to 1N 4007.Scan.jpg
 

Thread Starter

axisus

Joined Dec 18, 2019
3
I think that this will do it. With Fret SW open motor M will run in reverse
until arm or cam opens SW B, mouse gone & all power off; with F SW closed, relay, RY, reverses polarity to motor which then runs until mouse is out & SW A opens stopping motor, releasing F SW starts mouse retreat. Diodes general purpose 1A like 1N4001 to 1N 4007.View attachment 194895
Many thanks for that. It is totally over my head (!) but I'm sure I can find someone who can explain it to me in laymans terms.
 

Bernard

Joined Aug 7, 2008
5,397
Where do you buy your electronic parts ?
If you can power a light then you can power a relay & you are half way there.
Just for a comparison I'll throw in a servo control used to lift a shooting target.
 

Attachments

A small RC servo would work but a small DC gearhead motor will also work with simpler electronics. Just as an example, from All Electronics, USA, CAT # DCM, Model GA12-N20, 180 deg. in .3 sec. 3-12V, 1:10, 2kg cm @ 12V
15 X 12 X 10 mm. additional: 5 V relay, DPDT, 2 SPST NC SWs. , 2 diodes, & SP.ST fret SW
I don't think his F fret is a switch but one of many small metal bars laid into the neck of the instrument which effectively shortens the metal string to resonate at the correct note. Thus more circuitry is required to detect the use of the note.
 

Bernard

Joined Aug 7, 2008
5,397
A metallic string & a metallic bar if brought together makes a switch. Seems that the OP implied this.
How far out can the mouse come out with out getting his nose twitched by a string ? Maybe he could just slide up to the hole ?
 
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