1
\$\begingroup\$

So background: I have a novelty light up Disney Fantasia Sorcerer’s hat that I would like to use a a Christmas tree topper. The hat has an LED circuit built in with pulsating lights in various colors that is powered by 3 AAA batteries (4.5V DC). At the base of the hat is a normally open momentary switch button, one of those “Press Here” things. When you press the button the little LED show turns on with a couple colored LEDs pulsating on and off and a couple multicolor LEDs cycling colors and it lasts a little more than 30 seconds with just a single press of the button.

Since it is at the top of the tree I would like to be able to swap the battery pack for an AC adapter that I can plug into the end of the light string on the tree on a timer, so whenever the lights are on, the hat lights up. The problem I’m having is bypassing the little “Press Here” button to trick it into staying lit up whenever there is power. I tried cutting the switch off and twisting the wires together to provide a constant closed circuit but when I switch the battery pack on, nothing happens. When I take the two wires from the switch and briefly tap them together, the hat lights up. If I sit here and periodically tap the wires together, simulating the press of the button, I can get the hat to stay on indefinitely. But if I leave the wires in constant contact, the lights stay on for their 30 second show then turn off.

In the picture, I’m holding the two white wires from the little circuit board twisted together as well as the switch I cut off. The black and red wire from the top left of the board going out of the picture is the 4.5VDC from the battery pack. Circuit

\$\endgroup\$
8
  • \$\begingroup\$ With an ohmmeter, one side of switch may be Vbat (-or +) the other a high R logic input. There may be some clock to LED outputs that works or a cap to V+ added to Input for a reset, but insufficient detail to say for sure \$\endgroup\$ – Tony Stewart EE75 Nov 19 '20 at 15:37
  • \$\begingroup\$ A warm welcome to the site. please can you split up your question into paragraphs to make it easily readable. At the moment, it's a solid block of text. The better the quality of your question, the better the quality of the answers you will attract. Again, welcome. \$\endgroup\$ – TonyM Nov 19 '20 at 15:58
  • \$\begingroup\$ With power on, I get a very low resistance value (~3 Ohm) between Bat- and Lead 1 of the switch, and a voltage of 0.3V between Bat- and Lead 2. \$\endgroup\$ – Adam Marzec Nov 19 '20 at 16:01
  • \$\begingroup\$ After further probing with the multimeter, I know Lead 1 of the switch is ground \$\endgroup\$ – Adam Marzec Nov 19 '20 at 16:13
  • \$\begingroup\$ @AdamMarzec So you know that the switch temporarily pulls Lead 2 down to ground? And you want to do this every few seconds? I think the simplest type of circuit that does that is called a relaxation oscillator. In your case, you want a relaxation oscillator that can sink some current (but we don't know how much current will flow from Lead 2). \$\endgroup\$ – piojo Nov 19 '20 at 16:56
2
\$\begingroup\$

The most obvious solution is to build a little timer circuit that fires every 30 seconds and re-triggers the sorcerer's hat. It's a beginner-level build, but still involves a half-dozen parts and either a breadboard or soldering to connect the parts.

Instead, I would suggest a trick: you could try a "photoresistor" wired in parallel with the switch and placed right against one of the flashing lights. The idea is to create a self-retriggering action. Don't spring for a photocell assembly, such as used to trigger outdoor lights -- you want just the bare photoresistor. These are cheap ($3.99 for 30 pcs from Amazon). It might not work but I don't think it will harm your circuit either. If it doesn't work, go the timer route. enter image description here

\$\endgroup\$

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.