Napkin Launcher Project

Electronics
1

Hi all,
I’m a first year engineering student and I’m just trying to wet my feet in electronics builds. I am trying to build a pneumatic napkin launcher for a bit of fun with some of my friends and I just have a few questions so that I can build it.

Circuit
Circuit742×756 19 KB

  1. The only solenoid valves I can find are 12v so how can I supply it with enough voltage from (preferably) a 9V smoke alarm battery?
  2. The Micro controller is to make sure that the solenoid only opens for a fixed amount of time, and the input dial is to experiment and set that variable. What components would you recommend purchasing for this?
  3. Given the low energies involved, are these components even required. (is there anyway of running everything through the micro controller to bypass the relay)
  4. If there’s anything else I need to consider please let me know.

Thanks
Tony

2

You will need to protect the microcontroller with a diode or more probably probably use a MOSFET to drive the relay, for one thing.

3

Indeed you could use a logic level MOSFET like
IRL2703PBF which can be driven by the micro (3.3V or 5 v levels). I would suggest to use an Arduino if you are just starting. Maybe you want to use a LiPo battery and charger?

4

Solenoid needs more than voltage, it needs current, and the 9V smoke detector batter is unlikely to supply the necessary current even if you found a lower-voltage solenoid. @pauldg123’s suggestion of LiPo battery seems like a good one; they supply more current.

There are a lot of recent power MOSFETs now that can go full-on with GDS of 3V. The problem is that many of the good current options are surface-mount only. I use some that are 2mm x 3mm and have breakout boards so that I can use them to replace old TO-220 style through-hole MOSFETs. Note that while they have protection diodes inside, they aren’t necessarily enough for a solenoid; you’ll really want a “crowbar” diode to protect your MOSFET.

Then for a microcontroller you’ll need something that can take 12V. Arduino is a well-documented starting point that has a voltage regulator that can handle 12V.

Your “input dial” is a potentiometer, and it has three legs; voltage reference (relative to the voltage for your microcontroller’s ADC sense, likely 5V or 3V3), wiper that goes to the ADC pin on your microcontroller, and ground.

I’m sure this is full of stuff you don’t know yet, but google will help you look them up. :wink:

1 Like
5

Thanks, much appreciated.

6

You’re welcome!

Some useful resources: