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Thursday, November 29, 2018

Millivolt Source with Digital Potentiometer

Variable Parameters like voltage, current can be obtained by using a Digital Potentiometer. Microcontrollers or Counters operate FET CMOS Analog Switches. The switches configure resistor networks to adjust circuit performance. It could be a Speed Control of a Motor or Brightness of a Lamp. Volume controls and Tuners also can use this.

Millivolt Source with Digital Potentiometer

Description. - In this Circuit, digital potentiometer, connect pushbutton switches to fast and slow with one end to +7.5V, when you hold the button down the analog voltage will ramp up-down, fast or slow, this will enable you to make a digitally controlled millivolt source or power supply.

Digital Potentiometer - del50003

Here is a Millivolt Source i built for Calibration in the early days. It uses only CMOS Digital and Mixed Chips from Intersil and CD40xx Series.

Wednesday, November 28, 2018

Optical obstacle switch with LM567

This is a simple toy that has many applications. Any object that breaks a light beam will trigger a relay to on condition for a period of time.

Optical obstacle switch with LM567

Description - The 555 monostable has a 1 second period, If pin 2 gets low trigger pulses of a frequency more than 1 Hz, the output pin 3 will remain high, if the trigger pulses came in 10 second delays then output will go on and off, so also the relay and the electrical load on relay contacts. Like an integrator, it will not operate relay very fast. Even in a fridge stabilizer they put something like this else the compressor motor is damaged on frequent black-brown outs.

Optical obstacle switch - del50006

Now for the LM567 part, The clock at pin 5 flashes the IR Transmitter LED LD1 at a frequency set by C7-R5. The IR Photo Sensitive Diode or Transistor LD2 conducts when light is got from the IR LED. As the lights is in pulses, so also the impedance of LD2 goes low and high at same frequency. This develops an AC waveform across R3 over a DC representing Ambient light.

Tuesday, November 27, 2018

Solid-State Stabilizer Step up 110V AC

The circuit uses opto-coupler MOC3041 of Motorola and the Triac BTA16-600 of STMicro as a solid state switch or relay. Four Switches boost or buck the mains voltage, keeping output within limits.


It also uses the LM324 quad opamp from National Semiconductor which is low power and single supply. As the MOC3041 switches the Triac at zero crossover there is no inter-winding short of transformer on crossover hopefully, the control circuit is designed in such a way that more than one triac will not be turned on at a time, i would like you to give feedback.

Solid-State Stabilizer Step up 110V AC

The triac will switch at zero cross over because of MOC3041, hence no problem of an interwinding short, but then control circuit may fail or malfunction, so use fuse as shown . Also a snubber made of a 47E resistor and 0.02uF 630V pl cap in series must be placed across each triac.

Use heatsinks for all parts that heat, air circulation. Use Presets with series resistor as required so that you can test or calibrate. This Stabilizer should not be used with Inductive loads like motors or solenoids it may be ok for lighting and small electronics.