Tag Archives: circuit

Simple circuit indicates a low battery

@ edn.com writes:

The Design Idea in Figure 1 indicates a low-battery condition in an audio test instrument that is powered by four AA cells. As the instrument was otherwise an all-discrete design, this same approach seemed more in keeping with the spirit of the project than the use of a single-sourced integrated circuit.

Simple circuit indicates a low battery – [Link]

From Sand to Circuits – How Intel makes integrated circuits [PDF]


Here is a nice PDF document from Intel explaining how integrated circuits are made.

From Sand to Circuits – How Intel makes integrated circuits [PDF] – [Link]

Disconnect circuit for 12 volt lead acid and lithium batteries


KA7OEI designed a circuit that disconnects the battery when it over-discharges. He writes:

The avoidance of overcharging is usually pretty easy to avoid: Just use the appropriate charging system – but overdischarge is a bit more difficult, particularly if the battery packs in question don’t have a “protection board” with them.

Lead acid batteries (almost) never come with any sort of over-discharge protection – one must usually rely on the ability of the device being powered to turn itself off at too-low a voltage and hope that that threshold is sensible for the longevity of a 12 volt battery system.

Disconnect circuit for 12 volt lead acid and lithium batteries – [Link]

IRis – An Infrared Sensor using Photodiode amplification Circuit


[devttys0] designed a sensitive IR detector for capturing weak infrared signals. He shared in detail how he designed the circuit, beginning from the basic components, walking through solving the problems and finally ended up with a complete working circuit.

Craig Heffner/[devttys0] built this circuit for a friend’s Defcon talk, Blinded by the Light, the talk concerned about the emitted IR signals from the IR proximity detector in our devices like mobiles, and how we can identify the type of the device/OS using these signals.

Craig wanted to build a general purpose IR detector to capture and analysis the raw IR transmissions where IR receivers is designed to sense the modulated IR signals at 36-38 kHz. “But there is so much more to the world of IR than this” Craig said.

The first basic idea in the design is to use transimpedance amplifier which is basically a current-to-voltage converter.
When photons strike the photo diode, it will actually emit charge carriers, so the output of this sensor is a current. The output voltage (Vout= Ip*Rf) is linear in respect to the current.


The major problem with this particular configuration is the unwanted high frequency oscillation, so a capacitor was added in parallel with the feedback resistor.


The next problem solved by Craig, is the saturation of the amplifier in high and low side by adding some bias resistors just to keep the reference voltage of the positive input of the op-amp at just under 200 millivolts.

To prevent saturation in high side he added three diodes, in fact three JFETs configured as diode, in the feedback path. The reason of using JFET configured as a diode is that it has less leakage current than normal silicon diodes, so when the voltage exceeds 3*0.7=2.1V then they short the feedback resistor, this point is important in our design because it has a current flow from photo diode.

The last thing to solve in first stage of the design is the problem of constant current from ambient light, which will generate a DC component in the output. So Craig added a high pass filter in the output.


Now the circuit will still have some analog signals in output, noise and some negative spikes. So he cleaned things up by using a comparator with a Schottky diode in the non-inverting input to omit the negative pulses less than 0.2 Volt.


To see the full details of the design you can see the video below, and also you can reach the design files (SCH & PCB) over Github.

In addition, you can see the references pointed by Craig in his site analogzoo.

Iterated-map circuit creates chaos

DI5518f1Lars Keuninckx @ edn.com writes:

The Design Idea circuit shown below is a simple implementation of an iterated unimodal map, reminiscent of the logistic or Verhulst map encountered in the study of nonlinear dynamics. It is useful to show chaotic discrete-time dynamics to students, or as a random number generator. Specifically, the circuit implements: Vk+1 = rF(Vk), where F is a nonlinear unimodal function (a “bump”), implemented by the circuit in the dashed box. The response of this circuit is shown in the Vout vs. Vin plot.

Iterated-map circuit creates chaos – [Link]

HTML5 Circuit Simulator


Iain Sharp build this port of online Circuit Simulator based on Paul Falstad’s simulator, however Sharp’s version is built using HTML5 and requires no plugin to run. Think of it like animated Fritzing circuits, with a slew of pre-built circuits and components available for tinkering with.

HTML5 Circuit Simulator – [Link]

Making circuit boards with DLP projector


Nuri ERGİNER managed to create his own PCBs using a DLP projector and photo-resist dry film.

Every Maker like me dream a PCB printer which can quickly and precisely convert our electronic idea into a psychical circuit board. I know there are plenty of project going on the subject. (see the end of the article) What I tried here is something different, quick and precise. If you have lots of electronic idea in your mind and most of them have a high probability of fail, the system must be quick and easy.

Making circuit boards with DLP projector – [Link]

JIGMOD Electronic Circuit Building System


Succeed with your Innovations by building reliable, high quality electronic circuits. by JIGMOD:

Most electronic components aren’t compatible with breadboards. JIGMOD bridges the gap between those components and your breadboard.
Don’t work hard – work smart! Avoid wasted time spent debugging and troubleshooting.
Be amongst the first to use this revolutionary development platform.
Develop circuits with high quality, reliable results every time
Satisfy your curiosity easily
Succeed in your innovations
Maximize your ability to test and demonstrate your circuits

JIGMOD Electronic Circuit Building System – [Link]

Overheat/Overcooling Circuit Breaker

This project automatically switches off the electrical flow in event of excess heating or excess cooling thus protecting the circuit from damage using NXP NCX2220GU. The comparator guarantees to operate at low voltages which makes this device convenient for use in 5 V systems and has a typical internal hysteresis of 9 mV that allows for greater noise immunity.

For overheat circuit breaker, reference is set to a higher value. An NPN transistor is used to drive the relay since the initial output current of the comparator is not sufficient to drive RY1. When temperature is below the reference set, the output of the comparator will be low then the transistor is in the cut off state and consequently relay does not work. When temperature goes beyond the set reference value, the output of comparator becomes high. Thus biasing the transistor Q1, activating the relay and breaking the external circuit. For overcooling circuit breaker, reference is set below the surrounding temperature and PNP transistor is used. In default state, output of comparator is high but PNP transistor works as not gate as it does not gets biased at high voltage and consequently relay does not work. When temperature becomes lower than the set value, then output of comparator becomes low thereby biasing PNP transistor. Thus activating relay and breaking external circuit.

Overheat/overcooling circuit breaker has the primary objective of cost efficiency in providing circuit protection. Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset with no cost associated either manually or automatically to resume normal operation. Applications include isolation for all or part of the IT network switching rooms, thereby facilitating maintenance and protection for plants (transformers, generators, uninterruptible power supplies, and cables) from damage in the event of overcurrents.

Overheat/Overcooling Circuit Breaker – [Link]