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Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Archive for the ‘Hardware Development’ Category

LED Voltage Drops

Posted by jpluimers on 2019/09/19

[WayBackDangerous Prototypes: Basic Light Emitting Diode guide – Voltage drop or forward voltage has a nice table of common LED types:

You can also measure them yourself using most multi-meters have setting for that as described in [WayBack] Easy way to figure out a LED’s Vf in order to pick an appropriate resistor – Electrical Engineering Stack Exchange

You can also measure yourself, but my Proster VC99 multi-meter (cheap, but functions well, see for instance the review in [WayBack] MagPi issue 43) can measure voltage drop, so I’ve measured some LEDs from old PC cases:

  • Red: 1.8 V
  • Yellow: 1.8 V
  • Green: 1.8 V
  • Blue: does not measure

Given that they all have the same voltage drop, I made the below table with some resistor values to get the same current through them on various voltages (3.3V, 5V and 12V) based on Standard resistor values.

Note anything less than 20mA of current usually is OK (though 20mA often is on the bright side).

LED Colour Voltage drop (Vf) Total Voltage Remaining Voltage Resistance Ω Current mA Power mW
Any 1.8 5 3.2 220 14.55 46.55
Any 1.8 12 10.2 680 15.00 153.00
Any 1.8 3.3 1.5 100 15.00 22.50
Any 1.8 5 3.2 330 9.70 31.03
Any 1.8 12 10.2 1000 10.20 104.04
Any 1.8 3.3 1.5 150 10.00 15.00
Any 1.8 5 3.2 470 6.81 21.79
Any 1.8 12 10.2 1500 6.80 69.36
Any 1.8 3.3 1.5 220 6.82 10.23

Background for doing these calculations:


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Posted in Development, Hardware Development | Leave a Comment »

(53) Introducing the “Lab in a Box” Concept – Patrick Titiano & Kevin Hilman, BayLibre – YouTube

Posted by jpluimers on 2019/08/13

Related: Introducing The “Lab in a Box” Concept (ELC-E-2017-Prague).pdf



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Posted in Development, Hardware, Hardware Development, Hardware Interfacing, Power User, Raspberry Pi, Software Development | Leave a Comment »

Cable salad is of all times: 1964 analog computers; Moog syntesizers

Posted by jpluimers on 2019/08/01

This picture on Flickr of Engineer Karen Leadlay in an analog computer lab at General Dynamics, January 1964 shows that cable salad is of all times.

Atlas Collection Image


The above threads have really nice comments, including pointers to for instance the [WayBack] Moog synthesizer – Wikipedia  (lots of you remember the songs by Keith Emerson).


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Posted in Development, Fun, Hardware Development | Leave a Comment »

Sonoff Wireless Switch Family Gets a $3 IP66 Waterproof Enclosure

Posted by jpluimers on 2019/07/15

Interesting stuff from a while back that I will be using soon: [WayBack] Sonoff Wireless Switch Family Gets a $3 IP66 Waterproof Enclosure.

Pictures via CNX Software; originally found via [WayBack] $2.90 waterproof case for +ITEAD Studio Sonoff switches… – Jean-Luc Aufranc – Google+


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Posted in Development, ESP8266, Hardware Development, IoT Internet of Things, Network-and-equipment, Power User | Leave a Comment »

No IPMI? Use a Raspberry Pi to remotely control the power of your computer

Posted by jpluimers on 2019/07/12

Interesting project: [WayBack] WtRPM: A Web-based (Wt) suite to power up/down your computers –

It hooks a RaspberryPi to your ATX power supply.

Via: [WayBack] gpio – Use Raspberry Pi to control PC’s power switch – Raspberry Pi Stack Exchange


Posted in Development, Hardware Development, Hardware Interfacing, Raspberry Pi | Leave a Comment »

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