Servo: Recommendations for a wide sweep servo?

First – fantastic site! Great selection of products and information. Can anyone help me with a product enquiry?

Looking for a wide sweep servo (250 degree+ rotation).

I have a metering application - actually a physical gauge - to give you the idea, something like a 12" sized automobile speedometer. So, light duty, mechanism needs to drive a clock hand (or similar).

All the electronics are working fine and tested, using standard hobby servos. But the scale is not really wide enough. I am getting 180degrees (90 + 90) but I want 250degrees sweep (125 + 125). I need a reasonable accurate mechanism to show 200 steps.

Can you suggest best option?

I’ll need around 50 quantity, so if you can also suggest price and shipping to Europe I would appreciate.

Many thanks

PS If more suitable to use a small stepper with device to mark end travel (using slotted photo switch), or motor+gearbox with encoder, I’m open to suggestions, but it has to be simple to put together for our team.


Thank you for the compliment on our site! There are a number of options available to you. The simplest might be to use a servo with a larger range, such as our sail winch servo. This servo will turn just under one full rotation for the standard 1 to 2 ms range of servo pulses, and in our experience, you can actually get close to three full rotations if you exceed this standard range. However, with the increased range comes decreased angular resolution. When using a Micro Maestro to control one, we were able to get the sail winch servo to move in steps of less than one degree, which sounds like it would work for your application. If you are using a lower precision control source, however, such as an Arduino (just a guess given your user name), you might have a hard time getting the resolution you want. For a given control source, you can expect the resolution of the sail winch servo to be approximately four times worse than that of a standard servo that rotates 90 degrees over the range of 1 to 2 ms servo pulses.

Another option would be to mechanically increase the range of your standard servo using gears or by running a belt from a larger disk on the servo output to a smaller disk that controls your gauge. You will still lose resolution, but if you only need to increase the range from 180 degrees to 250 degrees, the hit to the resolution could be pretty small.

Finally, as you mentioned, you could use a stepper motor. The stepper motors we carry are all 200 full steps per full rotation, which doesn’t quite give you the resolution you’re looking for. You can get around this, though, If you use something like our A4983 stepper motor driver carrier, which allows for microstepping. Half-stepping or quarter-stepping might work for you.

- Ben