Let's Make Robots!

6DOF robot arm controlled by speech recognition or EMG

Listen to spoken commands or EMG and move accordingly

Construction of the arm

The arm is made from 2mm ABS sheet. This material is very easy to cut with a carpet knife, can be very well glued with superglue and be easily bent by warming it up with a hot air gun, so you can make your own brackets, etc.

As the Tower Pro SG90 is a little bit weak to act as a joint to the gripper I increased the locating surface to stabilize the servo horn:


Gripper design:



Parts assembled: 

Complete upper part assambled:  

Turn table using casters for furniture as support : 

Robot arm mounted on the base. The base is made from a piece of floor panel and then "coated" with 1mm ABS sheet. Floor panels are heavy, easy to cut and do not deform:


Power supply

Power supply design for the arm. The LM138 will need a heatsink. It is important to use 6V for the servos to squeeze out the biggest torque. At some movements the current consumption can easily exceed 3A, so it is not recommanded to use batteries.

Power supply, built on a perfboard:

Servo movements

Servos moving pretty fast (too fast) for a robot arm, which leads to big forces on some joints and parts, especially if the arm is fully extended. It seems to be a good approach to slow down the servo movements. Here is a simple code example how to do that:

servo 1,150
let w1=150
servopos 1,150
pause 100
for b0=1 to 50
let w1=w1+1
servopos 1,w1
pause 10
next b0
for b0=1 to 100
let w1=w1-1
servopos 1,w1
pause 10
next b0
for b0=1 to 50
let w1=w1+1
servopos 1,w1
pause 10
next b0
goto main


For first electromyography experiments I will use this circuit:

The schematic diagram of the electromyographic (EMG) amplifier is borrowed from this site.

The electrodes are made from 0.5 RMB coins, using common sticking plaster to attach them on my biceps and elbow:


Joystick control

Two joysticks from an old, damaged RC RX added to control the robot arm manually (see first video). I am planning to store different trained movements in an eeprom.

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Can't wait to see video of your electrocution EKGtrocution! Glad I have youtube again :P


The EMG prototype is so far working, try to make a video today. Next step is to switch a LED on and off with my biceps movements :)

Sorry, I saw you mention EKG in a previous reply and EKGtrocution sounded better :P



Markus, project is looking good so far.

the EMG is the real interesting twist here.   are those sensors attached to the muscles the same kind the medical world uses for an EKG machine? - little round stickers they place on your chest to monitor your heart?   seems very similar.

is this meant to be a remotely controlled arm where the EMG OpAmp circuit will detect human arm movement locally and send the commands to the robot arm somewhere else? 

Hi Paul,

Yes, the robot arm will be remotely controlled by my arm movements. The elektrodes are the same like for EKG.

Hey Markus, 

Nice project! I was following it from the shadows and I like how it progresses. I have some questions and some suggestions. First, what did you use to cut the ABS sheets. I know you mention is easy to cut with a knife, but the round parts? Second, and here comes my first suggestion, I have concerns about your power supply schematic, why don't you use a uBEC (about $5-15 from HobbyKing, depending on amperage) that is a switching power regulator for servos and can supply regulated 5V or 6V to your electronics and servos. If you chose 6V, then you can use a 5V LDO voltage regulator for your electronics or just a couple of diodes in series, since the electronics (microcontroller, sensors....) don't need more than half an amp. Since you need about 5 amps at max torque (4 standard size plus 2 micro size) you can go for a 5A uBEC. I am using this one for my 12 (mini) servos quadruped. Also, do you want to test out my µServotino for this project?


Hi Ro-Bot-X

Round parts are also easy to cut, but you need a stencil. Use then only the carpet knife point. You can also cut round parts with scissors. I cut the turn table in this way. To make them perfect round you can put a screw thru the center, clamp the screw like a drill in a column drill and treat the rotating part with sand paper.

I do not have concerns about my power supply. I need the 5V also for other applications on the arm (I'll add a LCD, etc.) and I have the LM138 and 7805 already, but your tip is a good one, I was not aware of uBEC.

I want to use your µServotino for one of my next projects, a RHEX :)

I really liked the arm design.Quite simple though looks effective.

waiting for the speech control to be installed and see the arm obeying its first order given by its master


I'll experiment with speech control and electromyography (EMG) :)

Next step is to build the voltage regulator circuit, based on a LM138 (5A).

great project hope to see some video