The Air Blaster circuit consists of a Feather RP2040 Prop-Maker that reads a VL53L1X time-of-flight distance sensor over I2C to determine when to fire. The Power Relay FeatherWing connects to the Feather over pin 10 to control the external 12V DC power to the solenoid valve. The solenoid valve is has a capacitor connected across its leads to preven EMF backcharge from resetting the board.
Headers
First, solder male header pins under the Feather and FeatherWing and female header sockets to the top of the FeatherWing Doubler. This guide has more info on soldering headers.
Relay Jumper
Not an exciting new track and field event, but instead, an invitation to solder one of the pads on the underside of the Power Relay FeatherWing.
I've chosen to solder the pin 10 jumper here.
Connect Feather/FeatherWing to Doubler
Press the Feather and FeatherWing into the Doubler as shown here.
Power Connection
Connect a 4" length of 24 ga. stranded hook-up wire, red and black respectively, to the + and - of the DC power jack.
Open the levers on the snap-action block and insert the legs of the capacitor as shown, then snap the levers shut.
Connect the red wire from the DC power jack to the center common screw terminal on the relay FeatherWing.
Then, insert the black wire from the DC power jack into one of the blocks of the snap-action connector that is already connected to the negative leg of the capacitor.
Run an 8" length of red wire from the normally-open (NO) terminal of the relay to a block on the positive wire connector.
Solenoid Connection
Connect one wire from the solenoid valve to the positive side of the snap-action connector block and the other solenoid wire to the negative side. Polarity usually doesn't matter for the solenoid, it should function properly regardless of polarity.
Test Run
Without pressurizing the air tank you can test if the solenoid triggers properly.
Connect the distance sensor to the Feather with the STEMMA QT cable.
Plug in the 12VDC power supply to AC wall power, then plug the barrel jack into the 2.1mm adapter.
Give the Feather power over USB (or battery as shown here for convenience).
Trip the distance sensor and the solenoid should open and close!
Enclosure
You can neaten up the build by placing the circuit in an enclosure.
Disconnect the solenoid from the wire blocks, feed them through a cable gland, and then reconnect as shown.
I sadly lost one cable gland, but if you haven't, use the second one for the STEMMA QT cable, USB C cable, and 12V DC power!
Connect Enclosure
Use zip ties or other fasteners to connect the enclosure to the handle of the air tank.
You can position the distance sensor wherever it makes the most sense for your haunt use. Some Blu-Tack will work fine, or make it a little more secure with double-stick foam tape -- or mount it to a structure with the mounting holes.
Page last edited October 16, 2024
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