Guide: How to make a 9g micro servo continuous

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Category : Arduino, Electronics

It’s always good to have servos that works like a geared motor. That also can go in both direction and speed is adjustable, it’s very handy in robotic project or general vehicles. The servo I’m using is a Mystery Micro Servo 9g SD90. But most of these small servos got the same internals so I guess you can use this on other servos.

1. Remove the stickers on both sides, and unscrew the four long screws that goes from the bottom to the top. One in each corner of the servo.

2. Gently lift off the top cover to uncover all the gears. Notice, it’s smart to remember the correct order of the gears, so that when you put them back you know what goes where. But I took a picture close to make it easier to remember where they all go. Use picture below for this purpose.

3. Remove all gears, no need to clean the grease off. Just put them in a box just for now.

4. Take the top gear and snip the little plastic bit off it, look at pictures below. This is the part that stop the servo from going more than 180 degrees.

5. Now we need to glue the potmeter, look at picture below. Just remove the plastic cap thats on the shaft of the potmeter to show it’s internals.

6. Attach the servo to the ardunio, using pin 9 as the signal. Use this program or just some other program that gives the servo 90 degrees. If the potmeter is centered the servo should stop the motor from turning, if it doesn’t try to turn the potmeter shaft one or the other way until it stops. You now got it centered so that 90 is stop, just add some glue to the internals of the potmeter to keep it locked. Before moving onto step 7 let the glue dry.

7. You now need to cut off the end of the potmeter shaft, this keeps the potmeter shaft from moving. Look at picture below for more info.

8. Now you only need to put it all back together. Just use the picture in step 2 for reference when adding all the gears.

There you are, now it should work like a continous servo. Any questions just leave a comment below.

Video of the final product:

Comments (8)

Great guide, my mod worked first time.
The decent level of speed control available is an unexpected bonus 🙂

Hello, sounds like a great mod. i don’t have an arduino and was wondering whether using an rc transmitter/receiver and centering the stick on the transmitter would be fine to get the 90 degrees point.

Hi..what is the +,- and signal wire color ?

you didnt told to make micro servo

when adjusting the poti to 0-position the motor stops for a few seconds, but then moves on at full speed again.
and i just can’t get it to switch directions via arduino.

Hi stig!

I do not understand step 5 and 7 on tutorial “How to make a 9g micro servo continuous”, can u make a video tutorial or send me an email with more information?

Thanks in advance, and sorry for my bad english.

Btw great blog! 🙂

and sorry for double post…

[…] som det kallas. Mina Mystery 9G var mycket enkla att modifiera, speciellt då det finns en bra guide att följa. Det gick inte bara bra hela tiden, jag råkade slita lite för hårt i ett av servona […]

[…] som det kallas. Mina Mystery 9G var mycket enkla att modifiera, speciellt då det finns en bra guide att följa. Det gick inte bara bra hela tiden, jag råkade slita lite för hårt i ett av servona […]

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