Mini candy grabber?

[Crowley]

Hey I've been looking all over for a tutorial of one of these things.

http://www.gadgetbargains.com/fm-jb-014.html?referrer=google

I guess like one of these, but I wanna home make it. Do any of you have any idea of how i can make one of these things? It'd be pretty cool to have next to my arcade corner.

Thanks!

Crowley

[jdjuggler]

Great idea.  That one you had the link for - looks cheap.  I'm not sure how the real ones work... But, I'd imagine that there's one rail which the motorized grabber rides on for one axis.  And the other axis may have to move the enitire rail perpendular to the first.  The 3rd control would be another motor controlling the up/down of the grabber string.  And possible a servo to control the grabbing actions.
Of course, there's a lot of "automatic" things that happen.
Grabber squeezing it's prey
Grabber moving back up.
Grabber going back to its "home" position.
Grabber letting go of it's goodies.

I'm sure if you used a PC this could all be written in you favorite programming language.  But, that's my general idea of the whole thing.
JD

[Crowley]

Thanks man. Obviously, without a pc, I'd have to do a microchip. so are you suggesting I use regular spinning motors for this?

[Ed_McCarron]

Regular brushed motors can be easier to interface to than steppers.  If you are using a pic or somesuch, you'd need (input/output wise)

Outputs:

X rail motor drive
X rail motor direction
Y rail motor drive
Y rail motor direction
Z motor drive (winch)
Z motor direction
Claw close (assumes a solenoid)

Inputs:

4 directions
Drop button
Home X
Home Y
Home Z

15 total I/O.  A simple basic stamp type BS2 (16 I/O) should work like a champ.  Home X,Y,Z can be simple microswitches.  Joystick and PB, straight out of any arcade supply place.

Use the motor direction outputs to drive 3 h-bridge circuits (or relays) to handle the motor current.

Programming it should be easier than building it.

You can source the BS2 at:

http://www.parallax.com/detail.asp?product_id=BS2-IC

Theres smaller, cheaper pics out there, but for ease-of-learning, the BS2 is pretty good.

The main program loop would look something like this (pseudocode):

Read joystick
Move x&y motors in response to stick
When button pressed
Turn off x&y
activate z for a time period
turn off z
energize solenoid
retract z until home reached
activate x&y until x&y home reached
deenergize solenoid
loop back to start

If you decide to go that route, I can help you with the actual programming if you are not familiar.

[Crowley]

Thanks man, that helps. I have a couple questions... How would I create the axies? Would I take a screw type rod and a moving pod attached to the screw like axis? And like have the screw on a barring attached to the pod? I'm so confused...

[BobA]

Here is a pic of the guts of a crane machine.

[Ed_McCarron]

I don't think any of the commercial ones use lead screws.  Just a motorized trolley, rolling on steel rails.  I've seen 2 types - move the trolley with a timing belt (motor offboard) or put the motor on the trolley and use it to drive the wheels.

Use 2 trolleys.  One for left/right, and one for front/back.

[BobA]

If you are just building a candy grabber you could probably get away with just left and right movement.  The candy grabbers always grabbed until they caught a bunch.  I think the movement thru the hopper of the candy registered the payoff and disabled the claw.  Since you are not trying to get the head of a plush toy you don't have to be as accurate when you position the claw for a drop.

Just a thought to simplify the construction.

BobA

[Ed_McCarron]

Makes sense.  Just make the cab narrow enough so that theres always candy under the claw, and put the prize chute to one side.

Cuts the work down by close to half.

[PetitMorte]

Perhaps canabalizing the motor/rails from an *OLD* flatbed scanner, or a plotter might work.