Switchable Servostick Reversing Mechanism and Circuit

[Scottacus]

I have a 60 in 1 cab with a Magstick and I finally got tired of having to help folks playing the game try to find the just the right spot to switch back and forth between 4 and 8 way settings.  I looked around online and found good reviews here and elsewhere about the ServoStick so I ordered one minus the control board since I don't have a MAME setup to take full advantage of all of the board's capabilities.

Delivery of the ServoStick was extremely fast considering that it came fro the UK to US.  There were no instructions in the packaging so I needed a way to allow the user to flip a switch on the top of the control board to switch back and forth between 4 way and 8 way.  I thought about building a 555 timer circuit to control the motor but I had concerns about folks quickly switching back and forth between 4 and 8 way before the timers had a chance to fully run the motor in a cycle from one end of the traverse to another.  I figured that the arm could get stuck in some intermediate position between both ends of the arm traverse.  I decided that a mechanical and electrical setup that gave positive feedback to the circuit that the arm had fully run its course was the way to go.

I went to Radio Shack and picked up a DPDT switch as well as a couple of NC roller switches.  The roller switches were mounted on top of piece of maple and secured just behind the Servostick arm so that the arm contacted them shortly before the full length of travel..



The circuit that I built is this one:



I used LEDs as diodes and as you can see in the following video the LEDs "light" when they are forward biased.  This only occurs at the beginning of a traverse between 4 and 8 way positions, you can verify this by checking out the circuit diagram.  The motor for the ServoStick has quite a bit of torque to it so there is a single switch bounce at each end of the motor's travel.

YouTube video:

I also added lighted control buttons as well as a lighted joystick top.  The tracball lighting is detailed here http://forum.arcadecontrols.com/index.php/topic,148753.msg1551014.html#msg1551014.  The joystick LED was RBG so I installed a white LED into the top and I also had to tone down the brightness of the Button LEDs by adding resistors, here is the final product.



Now I need to get new graphics for the CP to spice things up...

[Scottacus]

I wasn't crazy about the amount of stress on the motor mount with the bounce-back at the end of the arm's run from end to end so I added a silicone diode into the motor circuit.  It drops the voltage by .7v which slowed the motor's traverse speed and made the end of travel less violent.  Here is a video of the new set-up: 

[05SRT4]

Awesome job man, so much smoother. Also the lighted buttons look sweet.

the Servo Stick I got never showed that much aggressiveness when switching.

[wxforecaster]

I have two joysticks each with a ServoStik connected to a single ServoStik PCB. In fact, I was just setting this up today, but haven't finished wiring in the USB cable. I set the PCB to hardware mode, and bought a simple single pole toggle (center position off) to switch between 4 and 8 way on both joysticks.

When I had emailed Andy a while back, I could have sworn he told me that these were self-limiting and then there wouldn't be any damage done by leaving a toggle switch in either position (since, like you, I wouldn't be able to see the actuator as mine are inside a cocktail machine.

Is that not the case?

[Scottacus]

There were no directions, schematic or other info sent with the ServoStick and there are only two wires going into the motor so it is not a stepper motor.  I took the safe route and chose to shut the power off to the motor, it would be great if it is self limiting but I can't tell that from what I have here...

[welash]

I have two joysticks each with a ServoStik connected to a single ServoStik PCB. In fact, I was just setting this up today, but haven't finished wiring in the USB cable. I set the PCB to hardware mode, and bought a simple single pole toggle (center position off) to switch between 4 and 8 way on both joysticks.

When I had emailed Andy a while back, I could have sworn he told me that these were self-limiting and then there wouldn't be any damage done by leaving a toggle switch in either position (since, like you, I wouldn't be able to see the actuator as mine are inside a cocktail machine.

Is that not the case?

I think the limiting is done in the control board and not the motor itself.  I would guess that Andy is monitoring the current draw of the motor to determine when it is at the end of travel.  I can't be sure, since I don't have one, but it seems like a nice piece of equipment.

[AndyWarne]

The above is absolutely not the way these are supposed to work!

We went to a lot of trouble to design a control board which cuts off the motor when it reaches the end of its travel and this should be used. It uses an analog to digital converter to accurately measure current profile of the motor during its travel and intelligently control it including re-trying in case of binding.

We cannot endorse the above setup at all unfortunately.

[JamesTKirk]

This brings up an important issue that has been holding me back a bit from building a 60 in 1 or similar variant (i.e. 200 in 1, 500 in 1 etc). I love the switching ability of the servostick on my MAME cabinets. Is there a "correct" way to use them on a non MAME cabinet that does not have a PC with software to tell the servos to change the restrictor plate?

[AndyWarne]

This brings up an important issue that has been holding me back a bit from building a 60 in 1 or similar variant (i.e. 200 in 1, 500 in 1 etc). I love the switching ability of the servostick on my MAME cabinets. Is there a "correct" way to use them on a non MAME cabinet that does not have a PC with software to tell the servos to change the restrictor plate?

Yes you can connect either 2 buttons or a toggle switch to the Servostik control board and set the board to hardware mode. USB is not then needed.