Powering a mini servo motor - Page 1
Forum section: electronics / beginners

author: MickeyB
author_rank: Newbie
timestamp: January 06, 2023, 07:32:12 pm
content: Need some help. Working on a kinetic art project. I want to use a universal ac/dc power adapter charger hooked up to a servo tester (ccpm servo master) to power a micro servo 3 pin JST PH 2mm motor. The motor is STEMMA connector compatible, so it will connect to the servo tester without a problem.I plan to use a female mini micro JST 2.0 PH 2-pin connector with #26AWG wire to go from the charger to the servo tester. I will set the motor to continuous run. At this time, I don’t want to use an Arduino board.I don’t want to use batteries.Spec. on the adjustable charger are:Max Output Power:12WOutput Voltage:12 V, 3 V, 4.5 V, 5 V, 6 V, 7.5 V, 9 VMaximum current:1.2AI want this to be a permanent set-up, so when the charger is plugged in, the motor will run.Questions;Any safety issue with this configuration? Wire size? Voltage?Any other better way to accomplish this?Thanks in advance. Newbie with all this stuff.

author: Benta
author_rank: Super Contributor
timestamp: January 06, 2023, 09:35:36 pm
content: Don't see any issues with the setup (I've no idea what STEMMA means). Standard in the RC world is the JR/Futuba connector system, which I expect your servo has.How you connect power the servo tester is up to you, I'd think that a BEC servo cable would be more to the point.Nominal voltage for RC servos is 4.8 V (4.5...6.0 V), so I would set the power supply to 5 V.Then it should work.

author: jpanhalt
author_rank: Super Contributor
timestamp: January 06, 2023, 11:59:56 pm
content: I would be concerned with your "servo tester." May of the early ones were based on Schmitt inverters or the 555 . They worked OK with older servos and only gave a little jitter, particularly near the endpoints. They are virtually unusable with modern digital servos of the past 20 years. Microcontroller based testers should be fine.

author: bidrohini
author_rank: Regular Contributor
timestamp: January 07, 2023, 07:13:54 am
content: Which particular servo are you using? Is it SG90?

author: Infraviolet
author_rank: Super Contributor
timestamp: January 07, 2023, 07:07:36 pm
content: "micro servo 3 pin JST PH 2mm motor" gives 9 gram servos when searched for. These sort of things won't take much current, even if loaded to their stall torque, and are happily driven from a crude PWM supply where position is set by the length of the desired pulse. Putting a constant or zero voltage on their control pin will usually have them sit at a static location, but without any holding torque to resist applied forces trying to change the position.

author: james_s
author_rank: Super Contributor
timestamp: January 07, 2023, 07:48:56 pm
content: Quote from: jpanhalt on January 06, 2023, 11:59:56 pmI don't see anything to suggest he's using an early one. The market is flooded with cheap servo testers, they work fine in my experience on every servo I've tried them with. I think they're all micro based now.

author: MickeyB
author_rank: Newbie
timestamp: January 07, 2023, 07:51:36 pm
content: Yes, using a Sg90 servo motor.

author: jpanhalt
author_rank: Super Contributor
timestamp: January 07, 2023, 08:10:59 pm
content: Quote from: james_s on January 07, 2023, 07:48:56 pmApparently the SG90 comes in both analog and digital versionQuote from: TowerProIn my experience, the servo tester makes a difference. At least it did with digital Hitec, JR, and similar top servos in my possession. The last servo I bought was in about 2012. I have boxes of them.I don't consider a note of caution based 70 years of RC experience as OT. It may save headaches. The TS didn't give any information originally about the servo or servo tester being used/considered. I don't see anything to suggest he is using a current version of tester that you presume to be micro based.

author: james_s
author_rank: Super Contributor
timestamp: January 08, 2023, 09:06:01 am
content: I didn't say it was OT, or in any way unwelcome. I just don't think it's likely he's going to run into a problem. The earliest servos I'm currently using are from 2014 and those servo testers that are all over ebay work fine with both analog and digital. If there is a problem I'd be curious to know the cause.

author: bidrohini
author_rank: Regular Contributor
timestamp: January 08, 2023, 12:56:13 pm
content: Quote from: MickeyB on January 07, 2023, 07:51:36 pmThe SG90 runs at 4.8V(approximately 5). Since you will not be using any Arduino or Microcontroller, you can connect the VCC and GND with those of any 5V DC power supply. The signal pin must be connected to any source of a pulse signal. You can do that with a 555 IC. Wire size is not a big issue here. The generic male to male breadboard jumper wires will work.