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Gel Blaster Tank Robot

Gel Blasters and Robots go hand in hand as the DJI Robomaster S1 has proven. Lets build a cheaper DIY DJI Robomaster S1!


I saw these two things and they just seemed to go together very well.


On the underside is a Raspberry Pi 3 B+ and an Adafruit Motor Hat

I used the proto area to connect some 90 degree headers for the servos


A micro switch was stock on the gun to close the circuit to the firing motor. This was replaced with a mosfet that can be controlled via GPIO. I used PWM at 100% and 0% duty cycle so I could use the same logic as what is controlling the servos.

This is a very nice mosfet module that includes a motor protection diode and an optically isolated mosfet driver.

XBOX Control

An xbox controller was used to control everything. This is the most simple way to control driving, aiming, and shooting.

Pulling the top trigger makes the mosfet pass current as you can see via the red LED.

This demo uses the PCA9685 PWM controller, which is the same chip that drives the adafruit motor board.


These Red JHX servos are supposed to be more powerful than your standard $5 MG99x servos.

These are model JX PDI-6221MG sold for around $13.

The mosfets inside are rated for 6A and -5.9A


The hopper was replaced to increase capacity. I found a piece of plastic used rubber bands to close the top and keep the gel balls from falling out.

The original hopper snaps onto the top of the gun and is removable so I replicated that design.

Gel Balls

The gel blaster shoots small polymer balls identical to "orbeez"

Board Connections

Page Revision History

2019-09-12 First Published