Drop voltages out of a power supply with a few Silicium diodes in a row, each one drops 0.7-0.8 Volt

Please read the description first, for the best and most complete information.

The video shows how I drop the output voltage of a standard 5 Volt supply (say made to serve consumer Hubs, small computer appliances for consumers, output = 5 Volt (exactly) and say 100 mA up to 1 Ampère) to a lower voltage, with the help of a few Silicon diodes in a row.

To serve a bunch of paralled white LEDS. Christmas lights.

Each Si diode in the row drops the 5 Volt output voltage with (say) 0,7 Volt to 0,8 Volt. That depends somewhat. On higher voltages applied to a Si diode the bandwidth gap gets somewhat more sharp/precise, though never out of its physical values somewhere in this voltage range.

We can say: 4 diodes drop the voltage to 4 x 0,7 Volt = 2.8 Volt.

Measured voltage: (after the 4 diodes in a row with a 5 Volt power supply) = 2,8 Volt to the LED string. With 3 diodes (instead of 4) in that row you will get a somewhat higher current and voltage, but I always stay on the safe side with these LED circuits.

Thus here to serve a bunch of 30 paralleled white LEDS, that were originally made to work on 3 x 1.5 Volt = 4.5 Volt, with a current in the order of 20 mA-100 mA or so, via a low value carbon film resistor, of 5 Ohm at 0.5 Watt. (Was measured, color code was Green-Brown-Gold-Gold).

Please note: the ideal voltage and current to supply a LED of whatever kind (Red, Green, White, yellow, orange) depends for a very big part (in Physics theory) on the color (!).

But LED technology has developed enormous during the past 10 years, thus it also (now) depends on properties to send out a big or small amount of light (Watts, Lumen = effective light on frequency/frequencies X in the white light spectrum). I cannot stress that enough.

This is about their different barrier voltages, given by laws of Quantum Physics. That is no secrecy, it only tells that quantisized amounts of energy are needed to drop electron X to another band in the atom, sometimes after being lifted via energy put on it outwards first, where it gives out a quantum of energy on frequency X (say: light) when it goes that way.

So a white LED needs another supply voltage (and current) compared to a Red or Green or Yellow LED. It also means that a LED circuit must be supplied via a constant current source.

High power White LEDS: a lot of current that must be controlled very precise (in relation to the supply voltage) to get out its maximum light. Say in an automotive application or whatever use.

My You Tube channel trailer is here:    • Radiofun232 on YouTube, find working & tes...  

Interested in certain electronic circuits? (Radio’s, audio amplifiers, audio pre-amps, audio filters, measuring devices to test transistors and (say) mosfets or (radio) coils or Shortwave and MW radio’s?

Go to my Channel Trailer (“Radiofun232 on YouTube”). Link: above.

Type there the keywords that you like (e.g. radio/audio / amplifiers / filter / Shortwave / Short Wave /test / testing) into the “looking glass” = search function” and give “enter”.

Via that you can find specific video’s (under the say 1600 published). In almost all video’s a schematic is showed, if so: it is a working and well tested electronic circuit.

Keywords (again): ”audio”, “radio”, “amplifier”, “filter”, “Shortwave”, “transistor”, “FET”, “oscillator”, “generator”, “switch”, “schmitt trigger” etc; so the electronic subject you are interested in.

My books about electronics & analog radio technology are available via the website of "LULU”, search for author “Ko Tilman” there. Or https://www.lulu.com/search?adult_aud... I keep all my YT videos constant actual. Search on YT and avoid my circuits that are republished, re-arranged, re-edited on other websites, giving not probable re-wiring, etc.

I take distance from all kinds of fake claims, made via republishing my circuits via the www.

Upload 10 November 2025.

Earlier video (31 october 2025) where I do the same things but there via a Ohms resistor is here    • Making a mains power supply 110/230 V at 5...