Servo angle of rotation

According to the spec, the Servo module should rotate for 140 degrees. However, it seems that it only rotates about 90 degrees or so. What did I miss?


Back in the olden days, it was the signal sent by the transmitter that limited the servos motion, up to the 140 degrees allowed mechanically. Check your transmitter settings, richg99

Hi @gvardi, @richg99,

You are right, the servo moves about 100 degrees.
But mechanically, without power connected it can move about 180 degrees.
When you connect power (5Volt) to it the control IC in the transmitter bit (an Attiny45 microcontroller) starts sending a train of pulses to the servo. These pulses set the servo on its initial start position, which is about 70 degrees.
When you apply a voltage between zero and +5 Volt on the SIG connection (using for example a dimmer bit), the width of these pulses is changed by this microcontroller and moves the servo, up to a position of 170 degrees, so the movement is about 170-70 = 100 degrees.
Also the swing mode moves the servo between 70 and 170 degrees.
See attached movement graph and the Littlebits Servo wiring diagram with the microcontroller.
Hope this answers your question! :smile:


Thanks @alexpikkert, this is very helpful.
Any ideas / black magic how to increase the angle of rotation?


Thanks @gvardi,
I think there is no way to alter the bit design…
But there is a project buzz topic about using a stepper motor.
Maybe you could use it, but it is not available (yet), it is “under prototype development” in the forum. @chris101 started this topic.
See Yet another new Bit ... (stepper motor)

Hiya Guy (@gvardi),

While you cannot (feasibly) reprogram the onboard Tiny45, you can give it a different motor to run. The motor used by the servo Bit has a native swing of 180 degrees. If you substitute a servo motor that turns 360 degrees, you will get more rotation out of it using the same Bit. It turns out that all of the Parallax servo motors (and many other “hobby” motors) are plug & pin compatible with the littleBits servo motor.

Take a look at my “other motor” thread: Wow! Servo Surprise!

WARNING: Adding a different servo motor to the servo Bit base may cause damage to your the Bit and other Bits in the circuit - attempt this at your own risk! (But I did it, and it works fine. It uses about 60 ma to turn the motor I used in that thread.)

A note on the Stepper Bit - it’s only a project at this point, but stay tuned. All the information is in the thread @alexpikkert mentioned, (and a ’Work in Progress’ Project), so you could make your own. It uses about $10-$15 worth of parts.

Have fun! All the moving things make this stuff so much fun!