Optocoupler speed-up also reduces power consumption


by Marian Stofka:

Standard optocoupler speed is limited mainly by the relatively slow response of the phototransistor. This Design Idea adds components to the LED drive side to speed things up.

R1 is the original LED resistor, as used before the extra circuitry was added. Here however, its value can be higher, as the turn-on speed is determined mainly by the added circuit. You can thus save power, and also drive the LED with a less powerful driver.

Optocoupler speed-up also reduces power consumption – [Link]


UT204 is able to measure DC current and also True RMS


Clamp multimeter UT204 measures reliably even in real conditions of nowadays mains supplies and for an affordable price moreover.

UT204 from company UNI-Trend is a near relative to the UT203. multimeter. Already UT203 provides a lot of user comfort and a very pleasant feature – measuring of a DC current without interrupting a measured circuit. However UT204 is different from its “weaker

Simple constant current driver for a high power LED


Elmars Ositis has been working on a simple constant current driver:

In my previous post, I slapped together a quick LED lighting solution for my workbench… but it is truly a hack. What I really want to do is make a simple constant current driver, so the power LEDs can be used in other projects. One of those projects is an LED swimming pool light. It needs to be running at maximum brightness and low cost.

After much digging and testing, I found a simple circuit using a power FET, an OP Amp and 0.5 ohm resistor.
This simple circuit accepts a VCC up to 32v (limited by the Op-Amp). The 78L05 regulator provides a stable 5v reference and R1 is a potentiometer serving as a voltage divider, with the output on pin 2 serving as a reference voltage for the basic LM358 Op-Amp.


Simple constant current driver for a high power LED – [Link]

Low-loss Step-down Regulator


by elektor.com:

Adding to their ever growing family of power supply regulators Linear Technology have introduced the LTC3807 step-down switching regulator DC/DC controller driving an all N-channel external synchronous power MOSFET stage. The chip uses a constant frequency current mode architecture allowing a phase-lockable frequency of up to 750 kHz.

The chip draws just 50 μA no-load quiescent current and an OPTI-LOOP compensation allows the transient response to be optimized over a wide range of output capacitance and ESR values. The LTC3807 features a precision 0.8 V reference and power-good output indicator.

Low-loss Step-down Regulator – [Link]

Solar battery charge controller


by embedded-lab.com:

This Arduino Nano controlled solar battery charger can charge a standard lead acid 12V battery and runs with 90% efficiency under 70ᵒC (158ᵒF). The circuit can take up to 24V input from the solar panels. The maximum power point tracking is implemented in the circuit by measuring the output voltage and current from the solar panel to get the maximum possible power from it.

Solar battery charge controller – [Link]

Reverse Engineering A Counterfeit 7805 Voltage Regulator


Ken Shirriff has a great post on his blog about reverse engineering how a 7805 voltage regulator works:

Under a microscope, a silicon chip is a mysterious world with puzzling shapes and meandering lines zigzagging around, as in the magnified image of a 7805 voltage regulator below. But if you study the chip closely, you can identify the transistors, resistors, diodes, and capacitors that make it work and even understand how these components function together. This article explains how the 7805 voltage regulator works, all the way down to how the transistors on the silicon operate. And while exploring the chip, I discovered that it is probably counterfeit.


Reverse Engineering A Counterfeit 7805 Voltage Regulator – [Link]

Infrared remote controlled light switch with ATTiny2313


by Vadim Panov:

Back when I was only starting to dabble in electronics, I needed a project that would meet the following requirements:
simple to make;
original (i.e. done entirely by myself from scratch);
containing a microcontroller;
and maybe the most important of all, useful. I’ve had enough devices I assembled just to dismantle the whole thing a month later.
The thing I came up with at the time was a light swich for my room controlled over an IR remote from TV. Remote that I had used RC-5 protocol, hence the firmware is suited for any RC-5 compatible remote.
Everyone is familiar to the everliving problem with switching the lights off in your room before going to bed and stumbling back across the room. The IR switch I describe here solves that problem, and I can definitely tell that this project was a success – I am still using it with no regret.

Infrared remote controlled light switch with ATTiny2313 – [Link]

2N2222 Phase Shift Oscillator


A stable single transistor sine wave generator, that works with many values of input voltage.  In PartSim you can easily change the value of the resistors and capacitors and observe the effect on the frequency of the oscillator.  If you are manually calculating the frequencies, make things simpler by keeping  the values of the resistors and capacitors equal (R5=R6=R7 and C1=C2=C3).  You can see in the simulation that it takes a while to begin oscillating, and in ideal conditions it would need a signal to start oscillating, however in practice, noise begins the process without it.

2N2222 Phase Shift Oscillator – [Link]

Code generator for custom Android/Arduino menus


by drmpf @ instructables.com:

The first instructable shows you how to use the free pfodDesigner available on GooglePlay to design Android menus to switch Ardunio outputs on and off from your Android mobile, without you having to write any program code at all. The Fish Tank picture above shows the example designed in this instructable.

The example project shown here is suitable for complete beginners. This instructable does not require any soldering and No coding experience is required.

Once you have finished this instructable you will be able to design whatever menus you need to switch Arduino outputs on and off. When you have completed the second instructable (to be posted later) you will be able to switch real things on and off from your Android mobile, via relays connected to Arduino’s digital outputs.

Code generator for custom Android/Arduino menus – [Link]