HackSpace_-_October_2019

FORGE

Step 5: Replace the final and middle gears
Replace the now-altered final gear, and then carefully
reseat the middle gear. Make sure that all of the
gears mesh as they are supposed to.

REMOVING THE CONTROL ELECTRONICS
With the gears sorted out, it’s time to remove the
circuit board motor controller, desolder the wires on
the PCB, and solder the power wires directly to the
terminals on the motor. Heat up your soldering iron
and do the following:

Step 1: Identify the wires and desolder the
control wire
There will be three wires. One, the control wire,
likely yellow (or white or orange), is for controlling
the electrical pulses that create the precision
movements of your servo. We won’t be connecting
that to anything. The other two, likely red and black,
are the power wires. Go ahead and, using your iron
and a solder sucker or solder wick, heat the solder
point on the control wire (yellow) and remove this
wire from the PCB.

Step 2: Desolder the power wires

Locate the solder points on the PCB for the red

and black power wires and desolder those. Also,

desolder the two short power wires from the PCB

that are currently attached to the motor terminals.

Step 3: Remove the PCB

With all three connections desoldered, you can now

remove the PCB from the servo housing. You won’t

be needing it here.

Step 4: Solder the power wires to the motor

Now, go ahead and solder the red and black wires

directly to the terminals on the DC motor. On your

motor, the polarity of the motor will likely be

indicated by a mark or colour letting you know which

terminal is negative or positive. Here, our positive

terminal is marked by a red dot.

Step 5: Put everything back together

With the PCB removed and the power wires

connected directly to the motor, it’s time to put

everything back together. Snap the top plate back on,

the bottom plate, and screw the assembly back

together with the four screws.

That’s it. You have transformed a servo motor

into a continuous rotation gear motor that you

can use with an off-board motor controller/MCU

in a robot drive train or similar application.

YOU’LL NEED

Standard hobby

servo motor

Small Phillips

screwdriver

Angle cutters

Small file

Soldering iron

and solder

Solder sucker or

solder wick

Left

The PCB and DC motor of the servo. All

three wires get desoldered from the PCB,

and the red and black wires get soldered

directly to the terminal on the motor

Above

The middle and final gears

removed and the mechanical

stop on the final gear about

to be snipped off

Because of the

popularity of servo

motor hacking to

create continuous

rotation motors,

many servo motor

makers now sell

versions of their

servos without the

electronics and the

mechanical stop.

These motors are

usually marked

‘Continuous

Rotation’ on the

motor casing.

QUICK TIP

These are usually held

together by four long

Phillips screws

”

”