Building a Guillotine

I want to build a kind of a Guillotine - a project that holds a weight, can let it free fall and can lift it again. Holding a weight of 20 gram and falling length of 20cm is OK, 100-200 gram is great.
The lifting process can be slow (2-3 seconds is Ok, max 67-7 seconds). Alternatively having a stack of a few weights and letting only 1 fall at a time is also good for me.

Do you have any ideas how to implement it with an Arduino?

An Arduino is needed. Nothing else?
Read the first topic "How to use this Forum".

Please describe the real project, what are you actually trying to do and what is the purpose ?

Humane ant killer?

Purely mechanical...hardly a need for a uC.

I am not trying to kill ants...
I need a uC for controlling the timing of releasing the weight :
When a sensor detects that someone puts a hand below this Guillotine it release the weight. to his hand and then collects it up.
I've no idea how to implement the mechanical part with a motor.

Oh, You want to cut hands....
Sounds like further advice needs to be inhibited.

I want to to build a toy that taps on hands, my servos are way to weak for this (when I use a MG996R to move a 20cm straw against my hand I can't feel anything).That's why I want to use gravity with a 20g weight, just enough so that it is felt.

Okey. Hook on to that project using the MG996R and pull it further.

Here's my situation - I did some simple Arduino projects and programing, I look for some other direction instead of replacing the MG996R with a 100$ servo.

Why? Explain what You need that the old servo doesn't give You.

sounds like a vibrator of some sort might be more practical. Cell phone ringer/vibrators seem to be all over. The vibrator method is what a friend uses on a regular basis

saildude:
The vibrator method is what a friend uses on a regular basis

Mmm! :sunglasses:

Any time someone thinks up such a device i always think about the fate of Perillos of Athens

ROTFL

Seriously, why not just a gearmotor with a spiral cam disc, that lift the bar (or stick, or whatever) from a pin ? ... a microswitch or sensor can stop the motor when the pin is near the higher part of the cam, and the sensor for the hand just restart the motor, it roll the cam til the pin "fall" at the step and then relift it til the next stop cycle ... no servo needed, then ... :wink:

Using the word Guillotine was clearly a mistake...
I want to release a quick burst of energy (not much though, think of the energy of a high five), I couldn't get it with affordable servos and thought about piling up potential energy.

Etemenanki:
ROTFL

Seriously, why not just a gearmotor with a spiral cam disc, that lift the bar (or stick, or whatever) from a pin ? ... a microswitch or sensor can stop the motor when the pin is near the higher part of the cam, and the sensor for the hand just restart the motor, it roll the cam til the pin "fall" at the step and then relift it til the next stop cycle ... no servo needed, then ... :wink:

This sounds interesting. I didn't get it completely ,could you please explain more or drop here a link for a similar spiral cam disc project?

I don't know about other similar projects, is just an idea on the fly ... tried to draw something, but sorry, have nothing decent at home for draw (and my drawing skill is terrific too :P), anyway is just for give the idea ... using a switch and something on the cam or motor axis, you can stop the motor in the position where the lever is high and at the end of the spiral, so just restarting it, the lever fall, and then rise again til the next stop ...

bad draw.jpg

also no need for the lever made that way, can also just be used for lift something other ... with a 60 rpm gearmotor, you can have it relifted in a second, or 2 with 30rpm ... and there are realtively small and cheap gearmotors on ebay too ...

EDIT: maybe like these ones or similars, if the space is small ...

bad draw.jpg

Thanks a lot! This really helps me.