• Infrared Light

    10/02/2020 at 04:08 0 comments

    This article shows a simple infra remote control activated light. The maximum range can as long as 20 metres.

    You can see my circuit working in this video:

    I designed this circuit after reading those articles:




    I made my circuit with a traditional 6 V incandescent light bulb. However, you can use an LED light bulb or simply an LED matrix array. Keep in mind that LEDs conduct current in one direction. You can also used a 4.8 V krypton torch globe:


    Step 1: Design the Circuit

    I used the old PSpice software to quickly draw my circuit:

    Nowadays there are IR receivers that can work with power supply voltage between 2.5 V and 9 V, or even 20 V. Thus the diode and transistor power supply are optional. Also modern IR receivers have higher bandwidth and can thus receiver higher frequency signals.

    Step 2: Simulations

    The TTL power supply:

    The light bulbs is receiving 300 mA current that it needs:

    Step 3: Make the Circuit

    You can see the big MOSFET transistor attached the heat sink:

    I did not have high power 2.2 ohm high power resistors. Thus I used an alternative.

  • Funny Robot

    03/30/2020 at 10:15 0 comments

    This article presents a simple power transistor inverter and MOSFET motor driver:

    I designed a more simpler circuit to implement the control system in the following on Hack a Day article:


    You can see my circuit working in those videos:

    Second video:

    Step 1: Design the Circuit

    This is my circuit drawn in the old PSpice software:

    Later I modified the circuit to work with a Zener diode:

    This is a well known MOSFET motor driver circuit. It is used for H-bridge MOSFET circuits. However, this circuit might cost more money. You also have to be careful to make sure you not exceed the maximum gate voltage, the MOSFET input voltage.

    I also replaced the capacitors with a voltage regulator. Some voltage regulators might have a minimum input voltage above 3 V that I specified as a power supply for this circuit. Thus you might need to increase the power supply voltage.

    You can google MOSFETs on the internet. There is Depletion MOSFET and Enhancement MOSFET. There is a good quote on the internet about the difference of those two types of transistors:


    • Depletion Type   –   the transistor requires the Gate-Source voltage, (Vgs) to switch the device “OFF”. The depletion mode MOSFET is equivalent to a “Normally Closed” switch.
    • Enhancement Type   –   the transistor requires a Gate-Source voltage, (Vgs) to switch the device “ON”. The enhancement mode MOSFET is equivalent to a “Normally Open” switch.


    (Source: https://www.electronics-tutorials.ws/transistor/tran_6.html)

    I used Enhancement Type MOSFET.

    Step 2: Make the Circuit

    I used a 3.3 V Zener diode instead of 4.3 V Zener diode because this is what I had in stock. The use of a voltage regulator will prevent power loss caused by the 100 ohm Rz resistor.

    Step 3: Testing

    Testing video:

  • Simple Transistor Modulator

    03/30/2020 at 03:15 0 comments

    This publication shows how you can make a simple transistor modulator with just one transistor.

    The circuits presented in this article are similar to signal sampling circuits because simpel non-linear modulation signal processing is similar to sampling. However, those circuits do not allow linear modulation that was used in AM (Amplitude Modulation) radio.

    The period of the sampling signal is 100 us. Therefore the frequency is:

    f = 1 / T = 1 / 100 us = 1 / 100 * 1000,000 = 1 * 10,000 = 10 kHz

    This is ten times the input frequency of 1 kHz. Thus the signals would not overlap in frequency domain.

    Step 1: Design the Circuit

    Bipolar Junction Transistor Modulator

    The Q1 transistor acts a switch and saturates when the pulse signal is 1 V.

    MOSFET Transistor Modulator

    The MOSFET transistor acts a switch and saturates when the pulse signal is 1 V.

    Step 2: Simulations

    I used an old PSpice software for simulations:

    Bipolar Junction Transistor Modulator

    MOSFET Transistor Modulator

    The graph above is showing that the MOSFET transistor is not saturating. There must be something wrong with the MOSFET component model in the PSpice software student edition that I used. Usually MOSFET transistors would have a higher voltage current gain than the value specified in the model.