Archive for the ‘LED’ Category:

2018-12-04 FETs For Very Low Voltage Joule Thiefs

from FB group Building Transistor Radios 2018 Dec 4 Terry Harris I didn’t try to mimic the ALD, I used the FETs for a voltage booster. The typical 5mm LED needs somewhere around 60 mW for Max brightness. If I was powering it with 60 millivolts, it would require over an amp to get the

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2018-07-30 How Are LED Lights Made Dimmable?

From FB comment to Bill Sherman’s candelabra lamps. Bill Sherman Sometimes I wonder what is meant by dimmable. If a LED light uses hundreds of microfarads for the DC filter capacitor, then when the light is dimmed, the long time constant causes it to flash on and off when it is dimmed. So if the

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2018-02-14  LED 2nds, Factory Rejects

I’ve had several LED purchases that were LEDs of poor quality, actually factory rejects.  The sellers may not have known that the LEDs had “chipped chips” missing a piece, or bubbles or inclusions, but even more commonly, the LED chip is off center so the beam pattern is distorted.  I let the sellers know, and

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2018-01-22 Demo Of Wireless Charging

for FB group Electronics Hobbyists The demonstration of a wireless charging circuit that I built uses a Joule Thief circuit with two yellow LEDs in series.  The coil is a hand wound loop about 75 mm or 3 inches diameter.  A second loop of gray wire with a white LED (dimly lit at bottom) is

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2017-08-06 Seeing Digital Signals

From FB post about Arduino driving a ‘HC595 chip. You don’t need an oscilloscope to see digital signals.  If you slow down the speed, you can see what’s happening by looking at LEDs.  Everything is digital, just on or off. Plug two red LEDs, transistors, and current limiting resistors for LEDs (330 ohms), and for

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2017-01-18 Simulating An Analog Meter

A detector or discriminator in an electronic device might need to be adjusted to a very few points on a scale of a hundred or more points.  A digital indicator typically indicates only a fraction of that, possibly 16 points.  This is why the analog meter is still useful: it can indicate a small change

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2016-08-20 Blue Blinky Gets A Different Timing Capacitor

It has been a long time since I designed Blue Blinky; I just wanted to update it.  I have used a 1 uF electrolytic capacitor for the timing capacitor, and it works just fine with the two 680k resistors to give about 1 per second flash rate. I got a bag of hundreds of multilayer

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2016-02-23 Joule Thief With Daylight Shutoff

I designed my Blue Blinky with a daylight shutoff, using a LED as the light sensor and an additional transistor to amplify the minuscule current that the LED puts out.  This worked just great because there is the point across the timing capacitor where the current is very low, and it takes very little current

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2015-11-18 Flashlights Continued

After the 2015-10-26 blog, I searched for some other websites selling small flashlights and ended up at dxsoul.com, which is a part of Deal Extreme, DX.com.  I also found some reviews of other, cheaper flashlights, two of which were the Brinyte and the Tank007. On dx.com I found and ordered the the package called ‘Mini

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2015-10-30 LED Nightlights Are Poor Design

I found these at a Walmart store.  They’re named Great Value and came in a package of four nightlights.  As usual, curiosity made me open it up to see the circuit inside. I traced the circuit and drew a schematic of it.  I was disappointed, but not surprised.  The way the CdS photocell works is

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