I've been inspired and educated by Robothuts walking toys so I thought I would try to design one. This is a pin walker type design. I was trying for something small and simple so I designed it around a 6 Volt N20 gearmotor and two 2032 coin cells. The robot is approximately 110 MM tall and 70 MM wide and 40 MM deep(4.5" X 2.75" X 1.5"). The two 2032 coin cells are in the head along with 2 leds. I also wanted to try designing my own switch into the battery holder. The switch contact is made from a #1 paperclip. Make sure the #1 paperclip you choose will take solder. Since the shape of the contact is important I've included a jig for bending it. It walks pretty well with no tendacy to fall over. The arms are driven by the pins in the legs so they swing while its walking. I've seen that in a couple of Robothuts designs.

This walking mechanism is a pin in each leg driven up, down, back, and forth by a crank. This requires a crank and pin for each leg.The cranks are 180 degrees from each other. The gearmotor has a 3d printed 10 tooth gear on it's output shaft. This drives another 10 tooth gear with a 3 MM or .125" brass shaft. The shaft has a crank on it's other end. The driven gear and crank both have posts for driving the pins. The posts have to be approximately 180 degrees apart. You may have to drill the holes out for a good fit with the 3MM or .125" shaft.

The gearmotor I used was a 6 Volt 100 RPM N20 from Banggood. I really like these motors. They are quiet and have a low current draw. Using coin cells to drive motors is not the best practice but I was going for small and simple. A small rechargeable lion cell like the one used in small quad copters would probably fit in the head, but I didn't want to deal with battery chargers,low voltage cutoff, small connectors, etc. The CR2032 cells I've been using are from tea lights I bought on clearance from Wal Mart. I've used the same two through all the building and testing so far. That's short bursts of 10 to 20 seconds adding up to many minutes. They haven't gone flat yet but if you turn the robot on and let it walk for 30 seconds or so, the leds start dimming or going out in the parts of the walking cycle where the current is higher. This has to do with the voltage from the batteries dropping below the forward voltage of the leds wired in series. If you put your hand on top the robot making it more diificult for it to walk, the current draw will go up enough that the leds go off. Turning it off and letting it set well let the batteries recover. This is probably not a toy you would give to a child to play with for hours.

I have include a jig for soldering the leds and resistor so they will fit into the head. The end of the Youtube video has a slide show showing the assembly sequence and details.

Youtube video:
https://youtu.be/1caKmv_uRs0

3d printed parts:

head_main
head_base
frame
motor_clamp
arm1
arm2
leg1
leg2

crank
d_gear
m_gear

back_plate
front_plate

switch_jig
led_jig
switch1
switch2

pin X 2

parts:
number 1 paperclip
N20 6 Volt 100RPM gearmotor
3 MM or .125" shaft approx 30 MM or 1.125" long
2 leds
1K resistor
2 MM X 6 MM screw
3 MM screws 6MM and 12MM
3 MM washers

Update:
Added the Fusion 360 file

Thank you,
Rick

Folger Tech

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