Jinx wrote:
> I need to depress buttons on a keypad in order to run proof-of-
> concept simulations. The keypad is on a commercial unit, and
> opening it is not permitted. Not negotiable. Breaking the seal is
> big trouble
>
> Actuation force for the keypad is likely to be < 200g. I've not got
> it yet but judging by the previous manual use of ones like it, the
> force needed was about "average". I've measured the force for
> various remote controls, both button and membrane, and they're
> all in the range 100g - 200g. It will be a new unit so not expecting
> troublesome keys
>
> First thought was solenoids. Possibly the most sensible, but they
> are a touch on the expensive side (cost not really a big issue) and
> might be a little bulky to fit a dozen over a small keypad. Although
> rods could be attached so they could be staggered height-wise
>
> Second thought was levers operated by cams or pins on a rotatable
> drum (like a music box. Playing Dance Of The Sugar Plum Fairy not
> necessary ;-)) ). Somehow though the cams/pins would have to be
> withdrawn as the drum is rotated to position the cam/pin for the next
> key to be pressed
>
> Maybe a combination of both methods. Levers + solenoids
>
> I'd be interested in any other ideas. Still Googling
>
> TIA
>
> ===============================================
> If you aren't part of the solution, you're part of the precipitate
>
>   
For this application, I think solenoids with nylon or delrin probe ends 
would be the best
approach. To ease the problem of closeness, I'd either use a X-Y table 
to move the probe, or
make two probe stations, and only probe 1/2 at one time.

For some reason, there are millions of solenoids available on the 
surplus market. Many are on EBay, but others can be found at All 
Electronics and other surplus companies. I was looking yesterday and 
found a lot of 50 small solenoids for less than $1 each, as an example.

--Bob A
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