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Gizmo

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Location: Australia
Posts: 5119

Posted: 07:59am 22 Jul 2021

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Hiya.

I'm taking my CMM2 to a show and tell in a few weeks, and wanted to show off how easy it is to program and do real world stuff, like move a servo.

Can anyone suggest a generic cheap servo model thats a known worker on the CMM2? I do have some old RC servo's, but these are about 30 years old and ran on 6 volts, wasn't sure if these would be ok.

Thanks
Glenn

The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ

Volhout
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Posted: 10:34am 22 Jul 2021

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Hi Glenn,

I measured 4 different (modern digital) RC receivers, and they all output 3.3V logic signals to the servo's. This would imply that all modern servo's would work with the CMM2 (and CMM1).

I checked 5 different modern servo's (6gram/9gram/16gram/40gram/55gram) connected to pin 2(5V),6(gnd) and 12(PWM1A) to the CMM2, and they all work flawless. I also tested 2 older servo's (Futaba S3001 and Robbe S148 both 44 grams) on the CMM2 and these work also correct. However I would not guarantee the old ones (logic levels may be designed for 4.8V), but they do work).

All in all I think it is safe to use "any" servo on the CMM2.

One thing to bear in mind is the power consumption. If you use the 5V from the CMM2 you will have sufficient power to show they rotate (i.e. mount a indicator arm to them). But if you want to demonstrate something like moving weight, some servo's can draw several amperes of power. The USB power brick and internal wiring of the CMM2 may not be up to that (causing a restart of the CMM2..or smoke).

Regards,

Volhout

P.S. be aware there are also "low voltage" servo's that operate at 3.5...4.2V (1 lipo cell). These may burn out on 5V, and may not work on 3.3V. You cannot use these unless you power them from a lipo cell..
Edited 2021-07-22 20:37 by Volhout

PicomiteVGA PETSCII ROBOTS

Gizmo

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Posted: 05:15am 23 Jul 2021

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Thanks

I see Jaycar have some "Arduino Compatible" servos for $12, I'll grab one of those and give it a go. Its 3.5v to 6v.

The little demo will just be a servo and LDR. The Maximite will plot light intensity on a rolling graph on the screen and operate the servo when the light hits a threshold. Automatic light shade. The guys I'm showing have only ever seen Arduinos and some of them have never held a soldering iron, so I want to show off the Maximite as a good alternative for learning.

Last time I took in my old Microbee computer and some old Russian core memory. Spent the evening explaining on the whiteboard how core memory worked, good fun.

Glenn

The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ

Volhout
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Joined: 05/03/2018
Location: Netherlands
Posts: 5089

Posted: 06:38am 23 Jul 2021

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Hi Glenn,

If you mean this one it will be fine:
https://www.jaycar.com.au/arduino-compatible-9g-micro-servo-motor/p/YM2758

(I say so because there are also "constant rotation" servo's. These don't position, but act as a motor plus gearbox (no position feedback). These are used to construct small robots to drive the wheels. You don't want these in your project).

I am sure you'll have a lot of fun with the demo. I always liked giving presentations like these. On one occasion I took a microscope and just resistors... 100 watt, 10 watt, 1 watt, 2/4 watt, and then the SMD parts 1206, 0805, 0603, 0402, 0201 ....

The story behind it: how things get smaller and smaller. From the big tube radio's down to in-ear hearing aids.

Have Fun..

P.S. if you have 2 LDR's you can make a light tracker. With 4 LDR's and 2 servo's you can even make it dual axis. Like an air defense gun, or pointing solar cells to the sun. Just these parts, some wires, hotglue and cardboard. Of coarse a flashlight representing the plane or sun.
Edited 2021-07-23 16:43 by Volhout

PicomiteVGA PETSCII ROBOTS

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