Timer to lift block of wood then let it drop

[MJS]

Hi,

I need to build something to lift a bit of wood in response to a start event (e.g. a button press), and then 20 or so minutes later allow the wood to drop again (this can be a simple gravity drop).

The wood is thin and about 36" long x 6" wide - so not overly heavy. It is fixed to the sides of something at the back 2 corners (36" in-between) and then the front just drops until it hits the floor (roughly an angle of 45 degrees although this is probably irrelevant).

It's hard to describe - think of it as a sort of wooden cat flap that is mounted horizontally rather than vertically, so that the flap just drops down andd touches the ground! The idea is to lift the flap when a button is pressed, hold it up for 20 mins, then let it fall again.

Ideally this will be a smallish device (has to fit inside something) and will be low current & battery operated - although mains powered is possible if necessary.

I've no real experience of this kind of thing so am a bit stumped - can anyone offer any suggestions/help please?

 

[justDIY]

does it actually have to do the lifting, or like a trap, can you set it, and it'll hold for 20min and then release?

a simple solenoid and timer would be the easiest solution. energize the solenoid, set the timer, and presto

lifting could be done using a servo, a stepper or a basic DC motor

 

[HarveyH42]

Do you want it to drop on the cat's head, or avoid injuring the cat (matters to some people...).

 

[MJS]

Thanks Both.

At present it is just a plain old piece of wood - so it needs to be lifted, held up for 20 minutes and then released by whatever I am adding.

Whether or not the solution involves trapping the wood in the 'up' position and then later releasing it again is open to deisgn.

As for dropping, I can assure you nocat's will be injured in the making of this device lol

The wood is actually dropping and landing on more wood, for what it is worth. It isn't actually cat flap! It's an old-fashioned timed game from the 1930's. In the olden days, you'd pull a big long lever (which lifts the wood) to release the balls for the game and I think traps the wood open. It also pulls a spring and traps it with a metal bar. Then a clockwork timer works away, slowly moving a pole until it releases the spring enough to un-trap the door, allowing the wooden bar to drop and thus ending the game.

The problem is that the timers are well past their best, don't work properly and are practically impossible to get spares for. Because of their age and speciality, a working second-hand timer fetches 300 GBP or more!

I have seen versions of the game that have been converted to run from a battery powered button (and from a mains powered button) but obviously I have no idea how to do it.

 

[chiba]

There are many ways to do this, from modifying a simple mechanical timer to a fully pc controlled stepper motor setup. It would be easier if you gave us some more info..

How do you want it powerd, battery mains or mechanical? How heavy is the wood and how high is it lifted? got any pictures?

My best be would be pull the lever that lifts the wood and hits a microswitch, solonoid and 555 timer circuit.

If you got hold of a mechanical timer you could use the string to wind it to it's 20min mark and either use a solonoid release or mechanical release. I have an old mechanical/electro timer from a discarded microwave, that could work.

You could use a modified simple/cheap kitchen timer kind of like this:

**broken link removed**
**broken link removed**

 

[MJS]

Thanks for the reply.

I did touch upon power in the original post - preferably battery. Mains is possible if required. Mechanical not really an option as none of the original mechanism remains - not even the pull handle/lever.

The height the wood gets lifted needs to be at least 3 inches (more is ok).

I've no idea of the actual weight of the wood but the dimensions are as per the original post - 36" x 6" x approx 0.5" - so it isn't particualrly heavy.

No pics I'm afraid - it's currently away having some other work done to it.

 

[House0Fwax]

It's an old-fashioned timed game from the 1930's.

Is there any chance that you could elaborate on this ?
It sounds interesting, and with more info you may get more reasoned responses. I for one am trying to picture the item.