I assembled the circuit to see if I could come up with an alarm. Wanna make an Open Garage Door Indicator Alarm The circuit uses two transistors in a circuit that needs only a single timing capacitor and timing resistor to determine the frequency. It’s somewhat similar to the flasher circuits I’ve been working on,
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I did learn something from the Grease Spot Photometer Experiment. I found that the grease spot really does work. I can compare the brightness of two LEDs to find out the current in each LED. But then I realized that I don’t really need two LEDs (I didn’t use two with my luxmeter measurements). All
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I thought about doing this since I wrote a blog on it back in the mid 2000s. Use the Grease Spot Photometer Method to compare the outputs of LEDs. This experiment is used in Physics classes to demonstrate the relationship between candles and the distance to the light source. In my case I decided that
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I built this 1.5V to 9V DC-DC converter. It’s a modified Tim Williams design. It’s a Joule Thief with the output rectified and filtered, which is compared to the “Vref” zener diode and if the output voltage is too high, it turns off the base bias current to the Q2 driver transistor. The input is
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I had already built one of these several years ago, and since I’ve used it to test the crystals that I’ve salvaged. It’s a simple circuit, using only a single transistor to make a Colpitts Oscillator with the two leads for the inductor run to terminals so that various inductors and coils can be connected
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My “rival” Flagiusz has done some experimenting with a version of a Joule Thief which uses a capacitor similar to my Supercharged Joule thief, but is simpler. He also claimed that it was a bit more efficient than my SJT. This version, which he calls Fast Joule Thief, is the second one after the ‘basic’
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This schematic is from an old 1976 magazine. It uses germanium transistors, but the circuit looks to me like more common silicon transistors could be used instead. It uses a negative 12V supply, but I would use a positive supply, change the transistors, reverse the diode and use a non-polarized capacitor in place of the
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I my previous blog I determined that the Joule Thief flasher was not suitable as a flasher, but it was working well as a modified Joule Thief, with better efficiency than a conventional JT. I gave the schematic of the circuit, but I have made many modifications, so I decided to build a second one
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QS sent me a link to a Youtube video of a young lady who explained the use of a light bulb in a Wien Bridge Oscillator and who mentioned that HP long ago used a light bulb in its audio generator. The HP 200CD audio oscillator was a part of the workbench of a guy
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The schematic found here looks to me like it could be a good sound level meter with a few changes. One thing that it has going for it is the meter is inside of the feedback loop, so it will have a linear scale at low levels. Some meters don’t and the forward voltage of
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