Archive for January, 2013


The VIPer22A is low cost monolithic smart power devices with integrated PWM controller designed to operate in the wide range input voltage, from 90 to 264Vac.

The VIPer22A internal control circuit offers benefit such as: automatic burst mode in low load condition, overvoltage protection in hiccup mode, and large voltage range on the VDD pin.

This isolated VIPer22A constant current LED driver has been configured to drive 2 to 8 LEDs.

Big Motor Driver TLP250

Updated the schematic for those that want to save an I/O pin.  There is a Hex Inverter/Buffer circuit (U1) that feeds the inputs of the Optoisolator (U2).  If you look at the wiring for the Hex Inverter you will notice that the output of the second inverter feeds the input of the first inverter.  So, when a logic 1 is placed across pin-3 it is inverted into a logic 0 which turns off the Reverse Relay.  A logic 0 is also placed at the input of the first inverter which gets converted to a logic 1 on its output and turns on the Forward Relay.

By using the inverter circuit you will no longer have the capability for dynamic breaking.  In other words, one of the relays will be active as longs as powered is applied to the circuit.  Disabling the PWM signal will keep the motor from turning.

As suggested I changed the MOSFET driver to a TLP250 and dropped the 1K resistor across the Gate to source.

Update the schematic to show that the logic grounds are isolated from the dirty motor grounds.





The L7805CV is a three-terminal positive regulator. It is available in TO-220, TO-220FP, TO-220FM, TO-3 and D2PAK packages and several fixed output voltages, making it useful in a wide range of applications. The L7805CV can provide local on-card regulation, eliminating the distribution problems associated with single point regulation. The L7805CV employs internal current limiting, thermal shut-down and safe area protection, making it essentially indestructible. If adequate heat sinking is provided, the L7805CV can deliver over 1A output current. Although designed primarily as fixed voltage regulators, the L7805CV can be used with external components to obtain adjustable voltage and currents.


The BS170 is designed as one kind of N-channel enhancement mode field effect transistor which produced using Fairchild’s proprietary, high cell density, DMOS technology. These products have been designed to minimize on-state resistance while provide rugged, reliable, and fast switching performance. Features of the BS170 are:(1)high density cell design for low RDS(ON);(2)voltage controlled small signal switch;(3)rugged and reliable;(4)high saturation current capability.

The absolute maximum ratings of the BS170 can be summarized as:(1)drain-source voltage:60 V;(2)drain-gate voltage (RGS<1MΩ):60 V;(3)gate-source voltage:±20 V;(4)drain current-continuous:500 mA;(5)drain current-pulsed:1200 mA;(6)maximum power dissipation:830 mW;(7)derate above 25°C:6.6 mW/°C;(8)operating and storage temperature range:-55 to 150 °C;(9)maximum lead temperature for soldering purposes, 1/16″ from case for 10 seconds: 300°C;(10)thermal resistacne,junction-to-ambient:150°C/W;(11)drain-source breakdown voltage:60 V;(12)zero gate voltage drain current:0.5 μA;(13)gate-body leakage,forward:10 nA.If you want to know more information such as the electrical characteristics about the BS170,please download the datasheet in or .

6N137 Connection Diagram

Image6N137 Connection Diagram
A simple voltage-controlled oscillator (VCO), coupled to your instrumentation by an optoisolator, allows you to measure high voltages. The component values suit a 0- to 600-V input range (power dissipation in R1 and R2 set a limit on the input-voltage range). The circuit’s linearity is not an issue, because you can linearize its output in software.

The input voltage (V1), charges capacitor C1 until zener diode D1 conducts. Then, the zener diode triggers an “avalanche” circuit that discharges C1 into optocoupler Q1. After C1 discharges, the charging cycle repeats. C1 also averages the sensed-voltage level, which thereby provides noise immunity.

The optocoupler’s output is a pulse train whose frequency increases with increasing input voltage. To develop a linearizing equation for the circuit, measure its output at two convenient, widely spaced input voltages. Then plug the resulting periods into this second-order polynomial approximation and solve the two simultaneous equations for the two constants, k1 and k2:
Vz is the zener voltage of D1.

700W Amplifier Adjust the amplifier power 700W looks calm, but we requirement not put out of your mind to the adjustment happening forcing transistors, the whole relating to-engagement of frequency offset. It is compulsory to change the current insurance rule which serves to guard the final transistors. Their tendency to happen allowable to keep the transistors in the SOAR characteristics. primary it was needed to evaluate all the necessary resistors and subsequently measured to verify the accuracy of the calculations, it is managed with satisfactory results. Peripheral changes required in support of it to be there able to consistently amplifier to supply power. – First you need to restore the 2k2 resistors stylish string with the LEDs on Zenerovými resistors with upper wattage. be enough 1/2W resistors, power loss next to 80V +-based 1W. – therefore was traded 1k2 resistor in the pointer resistor by the side of 620 ohms.


Which is the initial reap has doubled, so at this point is the overall gain amplifier 40 and the limit excitation is sufficient to 1V rms. – Předbudiči transistors were replaced by stronger MJE15032/33 since KF467/470 are permitted satellite dish current 20mA – by the side of the exciter output stages are used the same transistors for example the output stage. – add up to of terminals of transistors has been increased to eight pairs – It had to occur to compensate designed for the excitation level by calculation a capacitor 10pF to 47pF + 22K appendage. This led to a slight “gradual” amplifiers, but this did not affect the ensuing parameters. This power is tuned correctly in support of this type of terminal transistors 2SA1943 /2SC5200.

With with the purpose of it is a least assessment next to which the amplifier operates stably exclusive of pass by the side of the rising and falling edges of the genuine.  The ultimate adjustment, the adjustment terminal current protection transistor. The SOAR transistor characteristics shows with the intention of the most allowable radio dish current once the voltage of 1.5 A is ideal in favor of cooling, so it’s essentially not as much of. Therefore, the current protection is customary to 12A, single-arm. This impersonate protection SOAR transistor characteristics. curt-circuit current is regarding 6 A which is about 075A for every transistor. This is far beneath the SOAR characteristics. The mechanical design is relatively clear-cut, the transistors are placed on the two cooling profiles with a height of 66 mm, width 44mm, overall part 260mm. They are twisted contrary to each one other in this way, from the cooling tunnel. Coolers are attaching the nylon aid which allows the compilation of transistors exclusive of washers, and thus better conveying tepla.DPS amplifier next to the top of the tunnel and the transistors are soldered from the underside of PCB.

ImageLM324N  Connection Diagram
    Transmitter operation. Operating power for the transmitter circuit is derived directly from the ac line. The dc power to operate the circuit is generated in two stages, one for an RE power-amplifier stage, and the second for the remainder of the circuit.

    The ac line voltage is applied to D1 , which half-wave rectifies the ac input . The resulting dc voltage (approximately 30V under load) is fed across an RC filter (comprised of R1 and C1) and used to operate amplifier, Q1. The second stage of the power supply (composed of LED1, R2, D2, D3, C2, and C3, which forms a regulated +13.6-V, center-tapped supply) feeds the remainder of the circuit. LED1 is connected in series with R2 and is used as a visual power-on indicator for the transmitter.

    An electret microphone element (MIC1) is used as the pick-up. The output of the microphone is ac coupled through C5 to UI-a (a noninverting op amp with a gain of about 100). The output of U1-a at pin 1 is ac coupled through C4 to the noninverting input of UI-b (which provides an additional gain of 48) at pin 5. The output of UI-b at pin 7 is then fed through D4 and RIO, and across R11 and C6 to the inverting input of UI-c which is biased to a positive voltage that is set by SENSITIVITY-control R19. This represents a threshold voltage at which the output of UI-c switches from high to low.

    During standby, the output of UI-c at pin 8 is held at about 12 V when the voltage developed across C6 is less than the bias-voltage setting at pin 10. When a sound of sufficient intensity and du-ration is detected, the voltage at pin 9 of UI-c exceeds the threshold level (set by R19), causing UI-c’s output at pin 8 at go low. That low is applied to pin 2 of U2 (a 555 oscillator/timer configured as a monostable multivibrator). This causes the output of U2 to go high for about one second, as de-termined by the time constant of R12 and C7. The output of U2 at pin 3 is applied to pin 4 of U3 (a second 555 oscillator/timer that is conftgured for astable operation, with a frequency of about 125 kHz). That causes U3 to oscillate, producing a near square-wave output that is used to drive Q1 into conduction. The output of Q1 is applied across a parallel-tuned circuit composed a T1’s primary and C8. The tuned circuit, in turn, reshapes the 125-kHz signal, causing a sine-wave-like signal to appear across both the primary and the secondary of Tl.

    The signal appearing at T1’s secondary (about 1 or 2 V peak-to-peak) is impressed across the ac power line, and is then distributed throughout the building without affecting other electrical appli-ances connected to the line. Transient suppressor D7 is included in the circuit to help protect Q1 from voltage spikes that might appear across the power line and be coupled to the circuit through T1.

    Receiver operation. Power for the receiver, as with the transmitter, is derived from a tradi-tional half-wave rectifier (D5). The resulting dc voltage is regulated to 27 V by D6 and R20, and is then filtered by C11 to provide a relatively clean, dc power source for the circuit. A light-emitting diode, LED2, connected in sGries with R20 provides a visual indication that the circuit is powered and ready to receive a signal.

    The 125-kHz signal is plucked from the ac line and coupled through R21 and C12 to a parallel-tuned LO circuit, consisting of C13 and L1. That LO circuit passes 125-kHz signals while attenuating all others. The 125-kHz signal is fed through C14 to the base of Q2 (which is configured as a high-gain linear amplifier), which boosts the relatively low amplitude of the 125-kHz signal. The RE out-put of Q2 is ac coupled to the base of Q3 through C15. Transistor Q3 acts as both an amplifier and detector. Because there is no bias voltage applied to the base of Q3, it remains cut off until driven by the amplified 125-kHz signal. When Q3 is forward biased, its collector voltage rises.

     Capacitor C16, connected across Q3’s collector resistor, filters the 125-kHz signal so that it is essentially dc. When the voltage at the collector of Q3 rises, Q4 is driven into conduction. That causes current to flow into piezo buzzer BZ1, producing a distinctive audio tone that alerts anyone within earshot that the baby needs attention.


The L7805CV is a three-terminal positive regulator. It is available in TO-220, TO-220FP, TO-220FM, TO-3 and D2PAK packages and several fixed output voltages, making it useful in a wide range of applications. The L7805CV can provide local on-card regulation, eliminating the distribution problems associated with single point regulation. The L7805CV employs internal current limiting, thermal shut-down and safe area protection, making it essentially indestructible. If adequate heat sinking is provided, the L7805CV can deliver over 1A output current. Although designed primarily as fixed voltage regulators, the L7805CV can be used with external components to obtain adjustable voltage and currents.
L7805CV absolute maximum ratings: (1)VI, DC Input Voltage: 35V for VO= 5 to 18V; 40V for VO= 20, 24V; (2)IO, Output Current: Internally Limited; (3)Ptot, Power Dissipation: Internally Limited; (4)Tstg, Storage Temperature Range: -65 to 150℃; (5)Top, Operating Junction Temperature Range: -55 to 150℃.
L7805CV features: (1)output current to 1.5A; (2)output voltages of 5; 5.2; 6; 8; 8.5; 9; 10; 12; 15; 18; 24V; (3)thermal overload protection; (4)short circuit protection; (5)output transition SOA protection.

Motorbike Alarm BS170

This simple to build alarm can be fitted in bikes to protect them from being stolen. The tiny circuit can be hidden anywhere, without any complicated wiring. Virtually, it suits all bikes as long as they have a battery. It doesn’t drain out the battery though as the standby current is zero. The hidden switch S1 can be a small push-to-on switch, or a reed switch with magnet, or any other similar simple arrangement. The circuit is designed around a couple of low-voltage MOSFETs configured as monostable timers. Motorbike key S2 is an ignition switch, while switch S3 is a tilt switch. Motorbike key S2 provides power supply to the gate of MOSFET T2, when turned on.

When you turn ignition off using key S2, you have approximately 15 seconds to get off the bike; this function is performed by resistor R6 to discharge capacitor C3. Thereafter, if anyone attempts to get on the bike or move it, the alarm sounds for approximately15 seconds and also disconnects the ignition circuit. During parking, hidden switch S1 is normally open and does not allow triggering of mosfet T1. But when someone starts the motorbike through ignition switch S2, MOSFET T2 triggers through diode D1 and resistor R5. Relay RL1 (12V, 2C/O) energises to activate the alarm (built around IC1) as well as to disconnect the ignition coil from the circuit. Disconnection of the ignition coil prevents generation of spark from the spark plug. Usually, there is a wire running from the alternator to the ignition coil, which has to be routed through one of the N/C1 contacts of relay RL1 as shown in Fig.1 Fig.2 shows the pin configurations of SCR BT169, MOSFET BS170 and transistor BC548.




Also, on disconnection of the coil, sound generator IC UM3561 (IC1) gets power supply through N/O2 contact of relay RL1. This drives the darlington pair built around T3 and T4 to produce the siren sound through loudspeaker LS1.  To start the vehicle, both hidden switch S1 and ignition key S2 should be switched on. Otherwise, the alarm will start sounding. Switching on S1 triggers SCR1, which, in turn, triggers MOSFET T1. MOSFET T1 is configured to disable MOSFET T2 from functioning. As a result, MOSFET T2 does not trigger and relay RL1 remains de-energised, alarm deactivated and ignition coil connected to the circuit.  Connection to the ignition coil helps in generation of spark from the spark plug. Keeping hidden switch S1 accessible only to the owner prevents the bike from pillaging. Tilt switch S3 prevents attempt to move the vehicle without starting it. Glass-and metal-bodied versions of the switch offer bounce-free switching and quick break action even when tilted slowly.

Unless otherwise stated, the angle by which the switch must be tilted to ensure the contact operation (operating angle), must be approximately 1.5 to 2 times the stated differential angle. The differential angle is the measure of the ‘just closed’ position to the ‘just open’ position. The tilt switch has characteristics like contacts make and break with vibration, return to the open state at rest, non-position sensitivity, inert gas and hermetic sealing for protection of contacts and tin-plated steel housing. If you find difficulty in getting the tilt switch, you may replace it with a reed switch (N/O) and a piece of magnet. The magnet and the reed switch should be mounted such that the contacts of the switch close when the bike stand is lifted up from rest.

4-Channel Pt100 Thermometer

The RTD or the Pt100 is one of the high accuracy temperature sensor for laboratory. Using the high resolution delta-sigma converter, enables designer to use a simple voltage divider circuit for measuring the resistance of the RTD without the need of any DC amplifications. This instrument shows how to use the LTC2420, 20-bit delta-sigma converter and the LM385 reference voltage for measuring four Pt100 sensors and displays on the text LCD.

 The circuit is simple voltage divider. VREF and R1 are fixed values. R2 is the Pt100 sensor. Its resistance is changed with temperature. We can measure the sensor’s resistance easily by detecting the voltage dropped across R2. The DC signal is equal to R2*(VREF/(R1+R2)). This signal can tie to the delta-sigma ADC directly.


 The MCU is 40-pin DIP package Microchip PIC18F4620 running with internal oscillator. The low power 32768Hz oscillator is for 1s time base. PORTB, PB0-PB7 are for LCD 4-bit interface. The display is 16×2 text LCD. Reference voltage, +1.2V is produced by D2, LM385. This reference voltage is tied to U2 , LTC2420 and U1A, LM358. U3, CD4051 is 8-channel voltage multiplexer. This project uses only 4-channel, X0, X1, X2 and X3. The signal from the sensor for each channel is measured by the dropped voltage across each Pt100 sensor.


 The sample sensor is a cheap two wires Pt100 sensor, WZP.

The firmware provides the mode for adjusting value for each channel, +/-5C with 0.1C step. When power up the instrument, keep pressing left key will enter the Calibrate Mode. We can select channel to be adjusted by pressing the left key. The center key is for increasing +0.1C and the right key is for decreasing -0.1C. The adjusting value will be saved to internal EEPROM. Recycle the power will exit this mode and will return to normal operation. Note that the firmware for converting the Pt100’s resistance to temperature is prepared for precision sensor. Thus for high accuracy Pt100, we can set all adjusting values to 0.0C.