I picked up some sample smart materials because I have a small project that I want to put 'magic glass' on the outside of so to speak.

I picked up a couple of different sample pieces from a couple different sources to try and one came with a AC adapter/converter to drive the 'clearing' of the smart film, the other came with a small battery operated unit.

Either one seems to clear the material, but throwing the testors on them produced different results.

The AC version (110vac US plug) seems to output ~17vac @ 60Hz. It also seems to clear the film a little better. The DC version (two AA batteries at 3VDC) outputs ~7.5vac @ 500Hz.

I'm not sure if this smart film needs specific frequencies or not, but this was a purchase off banggood of just a couple small sample pieces about 10cmx15cm each.

My project uses primarily 5vdc with access to low-current 3.3v sources. But I'm guessing this thing would draw too much current (for my 3.3v using the existing driver board) to clear all four panes even after I cut them down to fit inside the project.

So I'm guessing I need something that will generate an AC voltage in the 15v range somewhere between 50-500Hz to drive this thing but I know nothing about building oscillators or inverters. I would also prefer something that could run straight off a 5v source.

(I'm running out of room to put new DiY components. (I'm already stuffing a few props, a servo, a stepper motor, at least 25 LEDs, an i2c PWM board, ultrasonic vaporizor, and a a Raspberry Pi with a ReSpeaker shield a pair of speakers somehow inside of a 10"x6"x6" brass lantern! The smaller/simpler the circuit the better)

Any help is appreciated.

--EDIT 1-- the 110vac which outputs 17vac @ 60Hz is only about 1.4ma The 3VDC which outputs 7.5vac @ 500Hz is 7ma

  • \$\begingroup\$ Can you measure either the capacitance of the film or the AC current at both 50 Hz and 500 Hz? Please add that information to your original question. \$\endgroup\$ – Dwayne Reid Apr 17 '19 at 3:01
  • \$\begingroup\$ try running the DC version that you have from 5V \$\endgroup\$ – Jasen Apr 17 '19 at 3:11
  • \$\begingroup\$ I recall this diffused film becomes clear with 60Vac at line frequency in < 1 second. , frequency is not critical but draws more power with higher f., \$\endgroup\$ – Tony Stewart EE75 Apr 17 '19 at 3:17
  • \$\begingroup\$ @DwayneReid I think my meter will do current on AC as well as DC but I'll have to rig up something as it requires a through-connection in-line and the wires/connectors are soldered onto this thing. I have extra connectors but no hall-effect non-intrusive testing gear. I'll see if I can rig something up tomorrow to test the current and update the post. \$\endgroup\$ – Scott Wood Apr 17 '19 at 4:04
  • \$\begingroup\$ a royer inverter is simple. finding the right transformer to build one may be more difficult. \$\endgroup\$ – Jasen Apr 17 '19 at 4:05

Depending upon the AC current required by film, you MAY be able to use a MAX232 RS-232 driver chip to give you almost 20 Vp-p on the film. Initially, use a CMOS 555 timer chip as an oscillator. This will let you prove whether the RS-232 has sufficient drive.

If in fact the MAX-232 does work, you can probably persuade the MAX-232 to also be the oscillator. But no need to spend any time on that until you know that the MAX-232 will drive the film.

  • \$\begingroup\$ I swear I had found a circuit at one point because I ordered some op-amps for some reason and thought it was for that in case I needed it. I'm wondering if maybe a small neon driver may work also as there are some already built for USB. \$\endgroup\$ – Scott Wood Apr 17 '19 at 16:13
  • \$\begingroup\$ although now that I think of it, the op-amps were ordered in case I needed to make a circuit for the vaporizer. \$\endgroup\$ – Scott Wood Apr 17 '19 at 16:13

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