Power Circuit Diagram

The Power Circuit is comprised of three discrete components: the toggle circuit and the left and right power harnesses.

Toggle Circuit

Parts

• 22 AWG Solid Core Wire (Red, Black, Green, White, Blue, Yellow)
• 22 AWG Stranded Wire (White)
• 5 x 22 AWG Female Crimp Terminals
• 1 x D-type Flip Flop (CD4013BE)
• 1 x Reed Switch
• 1 x 3D Printed Reed Switch Holder
• 1 x Inverting Schmitt Trigger (CD40106B)
• 3 x 1kOhm Resitors
• 1 x 100kOhm Resitor
• 1 x 10Ohm Resistor
• 2 x .33uF Capacitors
• 1 x 4x6cm Solder Breadboard

Description

This is a circuit that toggles an output signal between 0 to +12V when the reed switch is activated by a magnet. The circuit utilizes a flip flop to change the input momentary signal from the reed switch to a toggle signal output. We use a signal debouncer on the reed switch to stop noise generated by the physical contact of the leads, then we use a Schmitt Trigger to further denoise the input into the flip flop. On powerup, the circuit defaults the signal output to 0V to assure the robot remains powered off. When properly assembled, this circuit guarantees a single toggle when a magnet is moved towards, then away from the reed switch.

Power Harnesses

Right Power Harness

Left Power Harness

Parts per harness

• 14 AWG Stranded Wire (Red & Black)
• 22 AWG Solid Core Wire (Black & Yellow (& Red for left harness ONLY))
• Heatshrink tubing
• Electrical Tape
• 1 x Female XT90 Connector
• 2 x 22 AWG Female Crimp Terminals (Right harness ONLY)
• 3 x 22 AWG Male Crimp Terminals (Left harness ONLY)
• 1 x Marine Fuse Holder
• 1 x 30Amp Fuse
• 1 x 100Amp N-Channel Mosfet
• 1 x 10kOhm Resistor

Description

A power harness controls the flow of electricity for its respective tube. Each tube has its own power system and is electrically isolated from the other tube, therefore, each tube must have its own power harness. Each power harness has an N-Channel Mosfet(essentially a voltage controlled switch) that electrically connects/disconnects power to the tube and a fuse to protect the electronics. The Mosfet has a Gate (Signal in), a Source (the (-) terminal of the battery), and a Drain (the load). The Gate and Source pins are connected with a 10kOhm resistor. The Mosfet will not turn on until a minimum positive voltage is supplied to the Gate pin.

Both the left and right power harnesses are essentially the same, except for their connectors. The right power harness has only two connections (Signal and Ground) with female terminators, while the left power harness has three connections (Signal, Ground and Power) with male terminators.

Assembly

This will cover assembling both the left and right power harnesses. Pay attention to left/right harness specific steps.

Step 1

Begin by soldering the 10kOhm resistor across the Gate and Source pins of the Mosfet.

Step 2

Next, cut approximately 4 inches of black 14 AWG wire and strip one end. Orient and solder the wire to the Drain pin of the Mosfet.

Step 3

For the LEFT HARNESS - Solder the fuse holder as closely to the positive terminal on the XT90 connector as possible. Our wire was about 1/3 of an inch long. Solder a 6 inch length of red 22 AWG solid core wire to the positive terminal of the XT90 connector (pictured below).

For the RIGHT HARNESS - Leave 1.5 inches of wire on the fuse holder, then solder it to the positive terminal of the XT90 connector (not pictured).

Step 4

Next we will connect the Source pin of the Mosfet to the negative terminal of the XT90 connector. To do this, place the Mosfet harness next to the fuse holder harness (pictured below).

Cut an appropriate length of black 14 AWG wire to bridge the gap. Strip both ends.

Solder one end of this wire to the Source pin on the Mosfet.

Step 5

Solder the other end of the bridging wire to the negative terminal of the XT90 connector (pictured below). Solder a 6 inch length of black 22 AWG wire to the negative terminal of the XT90 connector (not pictured).

Step 6

Solder a 6 inch length of yellow 22 AWG wire to the Gate pin of the Mosfet.

Step 7

The recommended assembly method is to apply a generous amount hot glue to the pins and connected wires instead of using electrical tape. The hot glue will help reduce strain on the Mosfet pins. See Design Improvements. The following pictures use electrical tape instead of hot glue.

Use electrical tape on the connection to the positive terminal of the XT90 connector as well.

Heatshrink the Mosfet.

Step 8

For the LEFT HARNESS - crimp and solder male crimp terminals to the 22 AWG red, yellow, and black wires. Heatshrink the crimp terminals.

For the RIGHT HARNESS - crimp and solder female crimp terminals to the 22 AWG black and yellow wires. Heatshrink the crimp terminals.

Step 9

Finally, solder the harness into the appropriate PDB.