USB PIC Programmer

DSCF2014-1024x768Stefano Purchiaroni rebuild a USB PIC Programmer that he found online. He writes:

This page is dedicated to everybody needs to program a PIC (Microchip) device via USB port. Looking on the web for ready-to-use projects, I found a good one called Open Programmer, coming with several schematics, PCBs and Open Source code. The original link is

What concerned me was the need to mount, on the mainboard, a specific socket board depending on the model of PIC being programmed. Moreover, the proposed layout did not meet my personal “compact look” ideas. So, I propose hereafter a small layout version of that circuit, adopting a single smart on-board ZIF socket. This version sacrifices many non-PIC microcontroller models. I will thank everybody proposing a larger range implementation, suitable to program Atmel and other devices. Anyway, if your goal is to program PIC devices, you are on the good site.

A small box, a USB connector, a ZIF socket, two leds. That’all in my compact proposal.

USB PIC Programmer -[Link]


Large Current Relay Driver


This is a large current Relay module with single pole double throw switch which provides normally closed and normally open operations. The Relay is the most common used module in application such as home automation, industrial automation, and machine on/off. Sometimes you need to control large current such as the fans, lights, water heaters, room heaters, Air-conditioning, vacuum pumps That is what this Large Current Relay Module can be helpful to drive such high current load with just TTL signal. Easy interface with embedded systems and micro-controllers.


  • Supply 12V DC
  • Current 190mA
  • Trigger Supply 3 to 8V DC
  • Optically isolated input for safety and noise immunity
  • 7 Pin Header for Inputs and 5V DC output
  • 3 Pin screw Terminals for Relay output

Large Current Relay Driver – [Link]

Passive Infrared Detector Circuit

The infrared (IR) is invisible radiant energy, electromagnetic radiation that we cannot see with our eyes, but we can sometimes feel on our skin as heat. The infrared light falls just outside the visible spectrum, beyond the edge of what we can see as red. Most of the thermal radiation emitted by objects near room temperature is infrared.

The circuit uses a MCP6032 microchip operational amplifier. The MCP6032 operational amplifier (op amp) has a gain bandwidth of 10kHz with a low typical operating current of 900nA and an offset voltage that is less than 150uV. The MCP6032 uses Microchip’s advanced CMOS technology, which provides low bias current, high-speed operation, high open-loop gain and rail-to-rail input and output swing. The MCP6032 operates with a single supply voltage that can be as low as 1.8V, while drawing less than 1uA of quiescent current. The MCP6032 is available in standard 8-lead SOIC and MSOP packages. It also includes, a PID20 integrated circuit and a few electronic components. The size of the output signal of PID20 is determined by the task at pins 3 and 4. The output signal at pin 3 is compared with a reference voltage equal to half the supply voltage. The reference voltage is taken from the voltage divider R2-R3-R4-R5. When approaching an object warmer than the surrounding environment, or to remove an object colder than the environment, the output voltage increases. The variation of the sensor output will be compared, the IC2a and IC2b, located voltage of 0.5V under and over voltage reference respectively. Depending on the output, one of the comparators calculates and activates T1.

This basic circuit is used in night-vision devices with infrared illumination, which allows people or animals to be observed without the observer being detected. The infrared light is also used in industrial, scientific, and medical applications as well as in consumer devices.

Passive Infrared Detector Circuit – [Link]

Hacking a Blood Pressure Monitor


by Eduardo @

I’ve been meaning to hack my blood pressure monitor for a while, and I finally got around to doing it! So, the idea is to mod a regular electronic blood pressure monitor to make it wireless and connected to the Internet, much like iHealth BP5 or Withings’. That makes detecting trends in your blood pressure much easier, since you can chart the data and even correlate it with other health data, such as how much sleep you’ve been getting, your weight or your level of activity. The model I have is the EW3106 from Panasonic. It’s quite old but from what I’ve seen the design hasn’t changed much throughout the years.

Hacking a Blood Pressure Monitor – [Link]


Touchscreen Arduino Library for XPT2046 Touch Controller Chip


XPT2046_Touchscreen is a library for the XPT2046 resistive touchscreen controllers used on many low cost TFT displays.

Touchscreen Arduino Library for XPT2046 Touch Controller Chip – [Link]

EEVblog #806 – Siglent SDG2000X Arb Function Generator First Look

Dave takes a look at the new Siglent SDG2122X / SDG2042X Arb Generator and compares it to the Rigol DG4162 and the older Siglent SDG5082.
1.2GS/s arb gen for US$499! Including some performance measurements on the Tektronix MDO3000 spectrum analyser.

EEVblog #806 – Siglent SDG2000X Arb Function Generator First Look – [Link]

The DigiRule – a digital ruler


Brad has designed a cool binary PCB ruler, The DigiRule:

So I made the DigiRule! – The DigiRule is a 15cm (6″) ruler with which is marked in binary digits rather than decimal. It has a number of built in digital functions including: logic gates, flip flops, counters etc.

The DigiRule – a digital ruler – [Link]



4 Channel Infrared (IR) Remote is a simple project using the popular  HT12A and HT12D encoder / decoder chips from Holtek.


  • Supply – Transmitter: 2.4 ~ 5 VDC, 5 V @ 20 mA & Receiver: 5 ~ 6 VDC, 5 V @ 50 mA
  •  Output – 4 Latched/Momentary TTL compatible outputs
  •  Crystal based oscillator for reliability of operation
  •  DIP switch selectable 8 bit address code
  •  LED output to indicate reception
  •  ON/OFF slide switch in the transmitter
  •  Power-On LED indicator in the Receiver / Transmitter
  •  High noise immunity
  •  Berg connector for interfacing of the board
  •  Four mounting holes of 3.2 mm each
  •  PCB dimensions – Transmitter: 61 mm x 47 mm & Receiver: 46 mm x 46 mm


Transient Voltage Suppressors

Voltage suppressors are used to protect circuits from unwanted transients, when other devices like diodes and capacitors fail to do so. Transient effects have various sources and are able to damage the connected parts and ICs if not properly measures taken. In this article we will discuss about the various transient voltage suppressors and their uses. We will cover, TVSs, Varistors, Multilayer Varistors, Surgestors and Polyswitches etc.

Bypass Capacitors


Bypass capacitors are very often used in logic and power systems to reduce unwanted voltages to reach ICs and other sensitive parts and to clean the power rails, but are limited to low power applications such as RC snubbers and decoupling of digital logic rails. For decoupling a digital rail a capacitor in the range of 0.01-0.22uF is often used and for decoupling a power rail a 0.1uF and up is used, connected form power line to ground. Capacitors are low cost, simple to apply, have fast action and are bipolar but have uneven suppression and may fail unpredictably.

Zener Diodes


Zener diodes are also used to protect sensitive circuits from unwanted voltages in a way of clamping low energy systems that run at high frequencies such as high speed data lines. They are low cost, fast in action, have specific clamping voltage, they are easy to be used and work bidirectional, but can only handle low energy and fail open (which can hurt the circuit). They are mostly used for regulation than transients.

Transient Voltage Suppressor Diodes (TVS)


Transient voltage suppressor diodes or TVSs are semiconductor devices used to clamp transient voltages and current, such as electrostatic discharge, inductive switching kickback, induced lighting surges etc. TVS are used for diversion or clamping in low voltage and low energy, modest frequency systems and are way more reliable than a diodes. They come in unipolar and bipolar versions. Unipolar TVS breaks down when the specified breakdown voltage is exceeded and pass current in one direction, in the opposite direction of the arrow. In contrast bipolar TVS can handle current in both directions. TVS are invisible to the circuit they are placed to until a transient appears. When a transient appears, TVS clamps instantly to limit the spike to a safe voltage level. The breakdown voltage of TVS should be selected to have a breakdown voltage greater than the working voltage of the circuit protecting. Some of the advantages of TVS is that they are fast, easy to use and fail with short-circuit. Some of the disadvantages is that their high capacitance limits the frequency they can be used, they can be used in low energy systems and are more expensive than Zener diodes and MOVs.

Metal Oxide Varistors (MOVs)


Metal oxide varistor or MOV is a bidirectional semiconductor device that acts like a voltage sensitive variable resistor. It’s made of various metal oxide p-n junctions placed in various directions and when the voltage across its leads exceeds a specified voltage they appear to have a very small resistance. The breakdown voltage is defined during the manufacturing process and can pass current in both directions, so can be used in DC and AC circuits. MOVs are fast, low cost, easy to use and handle more power than TVS. Also when they fail they short circuit. The disadvantage of MOVs is that they have moderate to high capacitance, thus limiting their use in lower frequency systems. MOVs are usually placed across mains input along with a series filter inductor and a fuse to protect the MOV itself. When a transient appears they switch from high resistance to low resistance this passing the excess current through. They can absorb a large amount of power for short periods of time and smaller amount of power for longer periods.

Multilayer Varistor (MLTV)


Multilayer Varistor or MLTV is a surface mount variation of MOV. Due to the surface mount contacts MLTVs have lower self-inductance and series resistance allowing for much quicker response times, typically less than 1 ns. The energy rating of MTLV are lower than other types of varistors but they can survive many thousands of strikes at full rated peak current. They are used on low voltage (3-70V) systems with modest frequencies. They are fast, compact and bidirectional, but more expensive than other MOVs and their high capacity limits their use on high frequency systems.



The surgector uses a silicon thyristor technology to provide bidirectional “crowbar” clamping action for transients. Surgectors remain in a reverse bias state as long as the voltage across is it is below breakdown voltage. If a transient voltage appears then the device breakdowns beginning the clamping action. If the transient voltage rises higher until the breakover voltage is reached a thyristor action is triggered and the surgector latches to ON state, thus short circuiting the transient voltage.



A polyswitch is a positive temperature coefficient resistor that stops the current from passing when a specified temperature is reached. In normal temperatures the resistance is low and current passes through easily. When the current rises enough (trip current) then resistance is increased dramatically and current flow drops. The polyswith will reset if the holding current is reduced and the device is cooled to normal temperatures. They often used in speakers, power supplies, battery packs, motors etc. They are low cost and easy to use, but requires a cooling down period to reset.

Avalance Diodes


Avalance diodes are designed to break down and conduct at a specified reverse-bias voltage. Their operation is similar of a Zener diode but the breakdown occurs using the avalance effect. Unlike Zener diodes, avalance diodes are available with high breakdown voltages as high as 4000V. They are placed in circuit in reverse biased direction and in this state they don’t interfere with the circuit. If the voltage across it exceeds the breakdown voltage then the diode passes the excess current to ground. Avalance diodes are often used in low voltage, high speed logic applications and are very fast (<1ns response). Also their shunt capacitance is low (50pF).

Gas discharge and Spark Gap TVSs

Gas discharge and spark gap TVSs are used for diversion of current in very high energy and high voltage applications. Their high energy capability can go up to 20kA and their leakage current is in pA range. Disadvantages of them is that cost more than other methods and are slow in response.

Transient Suppressor Examples Uses

TVS examples




MOV Example


MTLV Example


Surgector Example


PolySwitch Example