Blade Mechanism help

Hi, I've been trawling thru the site for about 4 hours now trying to find a simple way to make blades extend and retract. the problem is this, all the threads that suit my ideas the photos are no longer there!
Does any body have plans/details on how i can do this? I like the idea of motorised with the extend/retract switch mounted in the hand/glove. any help would be great. Also I'm in UK so knowing where to get the relevant parts would be a great help too.

hope you guys can help
 

Honus

Blooded
Here's what I would do. Use a decent speed servo with good torque- something like a Hitec HS-7966HB. Mount the servo on a linear slide. Attach a large drive gear (the largest you can fit in your gauntlet) to the servo and a gear rack on the fixed part of the slide- the larger the gear the greater distance the servo will travel. Attach your blades to the sliding servo.

Use a microcontroller (arduino) to control the servo using either a momentary push button switch or sensor. You could use all different kinds of sensors to activate it- bend sensor, RFID, muscle sensor, etc. Program it so when the sensor is activated the servo moves down to the other end of the slide, waits for a specific amount of time and then returns. Using this method you can make an animatronic gauntlet that is very light weight, is reasonably small and will have decent blade extension speed. Keep your blades as light weight as possible.

Never power a both servo and a microcontroller directly from the same battery. In this case I'd use a 3.3V microcontroller. I'd use AAA cells for their small size and power the servo directly from a 6V battery pack and then power the arduino from the battery pack using a 3.3V switching regulator. Pololu makes a nice small dirt cheap regulator. If you use a high voltage servo (7.4V) for more power then use a 7.2V battery pack (NiMH or NiCD cells) and use a 5V arduino with a 5V regulator. You can use a cheap linear regulator like a common 7805 but they waste a fair bit of power compared to a switching regulator and they need more voltage overhead (usually at least 2V) so when your battery pack voltage drops below 7V they don't work to well. You could use LiPO cells in order to save room and weight as long as you are aware of their limitations- I'd never use them without a fuse and a voltage cutoff circuit.

Servo drive gears are available from Servocity as are matching gear racks- use 32 pitch gears for strength. Low profile linear slides can be purchased from Igus. For an arduino I like the Sparkfun ProMini for it's small size and low cost (you will need an FTDI cable to program it.) The Adafruit Trinket boards are also good. As for how to hook up a sensor and program an arduino to move a servo have a look here (specifically check out steps 7 and 8) -

http://www.instructables.com/id/Arduino-animatronics-make-your-awesome-costumes-m/

Hope this helps!
 
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