1
\$\begingroup\$

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

\$\endgroup\$
  • \$\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 at 3:01
  • \$\begingroup\$ try running the DC version that you have from 5V \$\endgroup\$ – Jasen Apr 17 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\$ – Sunnyskyguy EE75 Apr 17 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 at 4:04
  • \$\begingroup\$ a royer inverter is simple. finding the right transformer to build one may be more difficult. \$\endgroup\$ – Jasen Apr 17 at 4:05
1
\$\begingroup\$

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.

\$\endgroup\$
  • \$\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 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 at 16:13

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.