I finally found the time and motivation to test the Pololu RC Switch with Small Low-Side MOSFET <http://www.pololu.com/product/2802> It works as expected. Bazooka Joe is now a little more bionic (strictly speaking he's more electronic, less electromechanical than he was).
The marker in RL001 <http://rctankcombat.com/rocket-launchers/RL001/> is a Spyder Imagine. A 9V battery powers a circuit board that drives a solenoid that flicks the sear to fire the marker. The trigger presses a SPST microswitch. According to my digital multimeter the microswitch passes a constant 480 uA (0.48 milliamps) when closed and one contact is at ground level (i.e. it's a low-side switch). I was surprised the current was so low, I guess it's driving a Darlington pair? I soldered a servo-style lead to the IN, VRC, and adjacent GND pins on the MOSFET board, and soldered a tiny link over the VRC and VCC pads to power the board from the R/C interface. I soldered a 2-position screw terminal block (with 0.1" pin spacing, very small!) to the LO and adjacent GND pins (on the "wrong" side because a surface-mount device was in the way on the "right" side). The marker has a pair of wires soldered to the trigger microswitch contacts and I connected the other ends of the wires to the screw terminals, making sure the ground side was connected correctly (GND pin to ground side of switch). When operational an indicator LED on the switch board blinks on briefly about once a second to indicate is has a signal. When the "fire" signal is sent the LED blinks off briefly about once a second and the marker fires with the first blink. The rate of fire (cycling the R/C signal to re-fire the marker) is "plenty fast" ... no specifics here because Bazooka Joe is a single-shot asset so rate of fire isn't an issue. Conclusion: I see at least 4 options for firing an electronic marker via R/C: 1. Ignore the electronics and use a servo with an arm or cam to mechanically move the trigger or the microswitch actuator. Pros: Simple, cheap, proven. You can see if it's working. Cons: The servo and arm/cam need to be aligned correctly with the trigger - needs mechanical engineering. Subject to wear-and-tear. 2. Use an R/C relay-based switch (examples include the PicoSwitch <https://www.dimensionengineering.com/products/picoswitch> and the Pololu RC Switch with Relay <http://www.pololu.com/product/2804>). I used the PicoSwitch previously and it worked fine (as long as the pulses weren't more than 500 ms either side of center, which shouldn't be a problem with typical R/C gear). Pros: Very small, easy to connect (polarity not an issue), voltage/current not an issue with typical markers, clicking sound confirms operation. Cons: Some soldering required for cheaper products (around $10), not for more expensive ones (around $20). Needs electrical and/or mechanical engineering. 3. Use a FET-based switch as above. Pros: Very small, LED shows status. Cons: Must get polarity right when connecting, some soldering required. Needs electrical engineering. 4. Given the low current I observed it wouldn't be a stretch to build a home-grown solution. A Pololu RC Switch with Digital Output <http://www.pololu.com/product/2801>, or a microprocessor (PIC <http://www.microchip.com/pagehandler/en-us/products/picmicrocontrollers>, PICAXE <http://www.picaxe.com/>, Arduino <http://www.arduino.cc/>, Raspberry Pi <http://www.raspberrypi.org/>, etc) with a resistor or two and a BJT or FET should do the trick. I'll look into this "someday". Pros: Customizable (e.g. with an MPU you can activate based on certain signal characteristic/s). Cheapish if the parts are lying around your junk box. Cons: Much assembly required. Needs electronic engineering. All these solutions are on the order of $10 or less if you can do some of the work, $20 or so if you just want to plug it in and go. -- -- You are currently subscribed to the "R/C Tank Combat" group. To post a message, send email to rctankcombat@googlegroups.com To unsubscribe, send email to rctankcombat+unsubscr...@googlegroups.com Visit the group at http://groups.google.com/group/rctankcombat --- You received this message because you are subscribed to the Google Groups "R/C Tank Combat" group. To unsubscribe from this group and stop receiving emails from it, send an email to rctankcombat+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
