Incorporating a PWM Control Module into a New Test Device

RE: Incorporating a PWM Control Module into a New Test Device

jw0752 — Mon, 01 Jul 2019 05:58:14 GMT

Since I have been having quite a bit of fun with this PWM Generator I decided to make a simpler version with just a 5 volt power supply and the module as well as output binding posts. This will give me the ability to test small servos and to have a second more portable unit to test with.

Here are some pictures of the build:

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The housing is a plastic box that I got at Walmart for a couple dollars.

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Here the unit is set to 50Hz and 7.2% Duty cycle which puts the servo at the 90 degree position.

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Side View. I did as good a job as possible on the strain relief considering the thin plastic case. The metal washer inside is glued to the box and spreads out the strain. [mention:8fb233e8974445138ef0af2b63b49f94:e9ed411860ed4f2ba0265705b8793d05] always pointed it out when my strain reliefs were not good enough. Thanks to his prodding I am much more conscious of this safety concern now.

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The power supply for the unit is just a board from a 1 amp USB power supply. I have removed it from its wall wart case and mounted it to the bottom with a standoff. The white post in the middle of the case is mounted to the bottom and provides extra support for the control module. It is necessary to push the control knob in order to cycle through the functions of the module and without the support pillar the top of the case would be flexed too much.

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Most of the modules that are available like this PWM module come with plastic fingers on either side that ramp into place and hold the modules into the front panel. These have never worked well for me as it is often difficult to get them to compress enough to fit through the panels. Recently I broke a front panel pushing one into place and subsequently I have begun to remove the fingers and to just glue the modules into the panels.

This unit is simple to build and does not require any expensive parts. Between the box, the USB power supply, the PWM module and the 3 binding post I believe that I have around $15 in this build.

John

RE: Incorporating a PWM Control Module into a New Test Device

jc2048 — Sat, 29 Jun 2019 09:25:49 GMT

Another interesting piece of test equipment.

Have you considered putting an H-bridge on the output? That would give you complementary push-pull outputs and extend the range of things you could do with it.

RE: Incorporating a PWM Control Module into a New Test Device

shabaz — Fri, 28 Jun 2019 23:56:39 GMT

Hi John,

Very interesting device! I can imagine it being very handy for working out hobby-servo-motor settings, with the PWM capability.

Excellent build as always.

RE: Incorporating a PWM Control Module into a New Test Device

DAB — Thu, 27 Jun 2019 01:38:01 GMT

Very good build John.

Well done.

DAB

RE: Incorporating a PWM Control Module into a New Test Device

michaelkellett — Wed, 26 Jun 2019 08:09:39 GMT

Nice blog John.

How much did you pay for the pulse gen module ?

Are you ready to make your own using a Nucleo board yet - then you could have all sorts of fancy pulse patterns and multiple outputs.

RE: Incorporating a PWM Control Module into a New Test Device

colporteur — Wed, 26 Jun 2019 03:26:08 GMT

I loved the narrative! You start with an idea, it morphs into something else, that fulfills the learning goal and adds additional value. I have a few of those myself and guess what, they make great stories.

Sean

RE: Incorporating a PWM Control Module into a New Test Device

genebren — Wed, 26 Jun 2019 03:16:01 GMT

John,

Nice blog. You sure can put together some very clean instruments. I hope that this serves you well in your servo motor testing.

Gene