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View Full Version : "Push & Hold" activation for Hasbro econo-boards



Don Se Wion
05-26-2011, 08:06 AM
One of the most annoying things, and probably the only one, about the cheap Hasbro boards is that while spinning the saber there is a very high chance to shut it off by mistake pressing the activation button. The source of this problem comes from the fact that the majority of the momentary switches used in sabers are very sensitive and even the lightest touch is able to turn on/off the board.

In order to solve this problem I tinkered a lot with my electronic spare parts and in the end I came up with the circuit I'm proposing you today. It's very simple in its design but does the job remarkably well.


http://i952.photobucket.com/albums/ae9/DonSeWion/PushHold.png

At rest the capacitor is maintained fully discharged by the momentary switch shorting it to ground through the Normally Closed pin.
When the momentary button is pushed, the capacitor begins to charge through the Normally Open and the resistor until it will reach the gate voltage threshold, causing the MOSFET to go in conductive mode. This way the SW+ coming from the Hasbro econo-board is shorted to ground triggering the activation.
As soon as the momentary button is released the capacitor is istantaneously discharged setting the circuit ready for another cycle.
Short and repeated pushes on the button like the ones occurring while spinning will not be able to charge the capacitor enough to trigger the activation, solving the whole problem.

A few considerations about the components:

- Trimmer -
In my prototype I used a fixed 130K resistor wich is requiring to hold the button about 1.5/2 seconds to activate/deactivate the blade.
Using the trimmer provides the ability to tweak the sensitivity of the circuit; the smaller the resistance the less time is needed to turn on the saber and vice versa.
The suggested value for the trimmer is 220K or 500K, at least this is what I found more commonly on the various online electronics stores.

- MOSFET -
For the MOSFET I'm suggesting to use the BS170 or 2N7002, however any small signal MOSFET will work.
In my prototype I used an IRF830 because was the only one around, but it was a real overkill for this application, expecially considering the volume restrictions we have to fit everything inside a hilt.

- Momentary switch -
The momentary AV switches sold here in the shop works very well in this circuit, but you can always use any other type making sure it has both NC and NO pins.
Momentary switches with NO only pin like the guarded one here can't be used because they don't reset the capacitor.

The circuit has been designed to work with the standard 4.5V/4.8V battery solutions commonly used with the cheap boards.

The only downside of this circuit is that when you are showing the saber around and someone is trying it for the first time you always receive the complain "it doesn't work" and you have to keep on repeating "hold the button and see" :)

I really hope that in this PC-L times someone will find this circuit useful.

Silver Serpent
05-26-2011, 08:28 AM
I'll admit I don't know a great deal about electronics, but this looks like a wonderful idea. Thank you for sharing this! It's definitely something to consider in future econo builds.