Dual DMX RC- servo driver - great for scan thru gratings

[dave]

Hey guys,

I have a new DMX board. This one is a dual DMX RC-servo driver, designed for moving diffraction gratings in front of a set of scanners. I have it set up so DMX values below 127 move the servo to one end of travel, and values above 127 move it to the other end. There are 2 trim pots to set the on position, 2 invert jumpers. No reason why one couldn't be used for non safety critical beam steering either

Introductory price $40AUD each plus shipping and GST if it is an Australian sale.





Example of mounting scan thru gratings

[polishedball]

These work amazing, I just haven't had time to write up a proper review. It will be coming.

[andyf97]

Damit; one day too late; I just ordered a load from another place.

http://northlightdmx.com/DMX512toRCservo.htm

[norty303]

Hmm, I wonder what it would be like using RC to control the servos. Certainly 1 less cable to run. 2.4ghz Rx are only £12 or so for my transmitter, it could be powered off the 5v PSU, and you can have multiple Rx bound to the same Tx, so 1 switch could run all gratings in all projectors.
OR even better, have them all on separate channels, but mapped to a single switch if need be, for individual control. The computer radios are quite advanced these days.

[kitatit]

Hmm, I wonder what it would be like using RC to control the servos. Certainly 1 less cable to run. 2.4ghz Rx are only £12 or so for my transmitter, it could be powered off the 5v PSU, and you can have multiple Rx bound to the same Tx, so 1 switch could run all gratings in all projectors.
OR even better, have them all on separate channels, but mapped to a single switch if need be, for individual control. The computer radios are quite advanced these days.

Hi Norty, sounds like a fun idea. I don't know the exact reason but when I've run servos powered via a switch mode power supply, they jitter and jump back and forth. Pretty sure it's to do with the high frequency switching in the supply. When I changed the supply to a battery source it disappeared due to it being a clean DC signal. Dave can probably explain the reason better.

Have fun
Kit

[dave]

Somewhat different Andy.. But thanks for your input, its always appreciated..

Damit; one day too late; I just ordered a load from another place.

[dave]

Sounds like noise in the smps.. Odd

Hi Norty, sounds like a fun idea. I don't know the exact reason but when I've run servos powered via a switch mode power supply, they jitter and jump back and forth. Pretty sure it's to do with the high frequency switching in the supply. When I changed the supply to a battery source it disappeared due to it being a clean DC signal. Dave can probably explain the reason better.

Have fun
Kit

[kitatit]

Sounds like noise in the smps.. Odd

Hey Dave,

Come to think of it, they have all been those simple 556 timer with a couple caps and resistors type drivers. I'd imagine they are much more susceptible to this than the smarts inside your driver. Is it because in these simple circuits, the voltages that drives the pwm width and pulse frequency are easly influenced by the supply voltage?

I imagine in your drivers because the pulses are generated by digital circuitry they are immune to this problem.

Bit off topic but it always bugged me not knowing why it happened. Do you know why?

[dave]

Hehe, I never had any joy with the 555/56 based circuits.

Hey Dave,

Come to think of it, they have all been those simple 556 timer with a couple caps and resistors type drivers. I'd imagine they are much more susceptible to this than the smarts inside your driver. Is it because in these simple circuits, the voltages that drives the pwm width and pulse frequency are easly influenced by the supply voltage?

I imagine in your drivers because the pulses are generated by digital circuitry they are immune to this problem.

Bit off topic but it always bugged me not knowing why it happened. Do you know why?

[dave]

I just found some surplus Chinese burst grating - works very well in a scanthru situation.



I have 1 x 1" piece already mounted to a small RC servo. Ill throw this in with the first sale

3 unused 1" square pieces I can sell for $20AUD each with a sale