4093 Schmidt Trigger / Fan Speed Regulation




Introduction: 4093 Schmidt Trigger / Fan Speed Regulation

About: Why would i buy something ready made when i can make it myself with half the features for twice the money? DIY!

If you have a fan that needs the speed regulated than a Schmidt Trigger such as this is one way to do it.

Basically a Schmidt trigger works with PWM pulse width modulation.
If you are really interested in knowing all the workings of Schmidt Trigger and PWM then check the links below.

Schmidt Trigger Wikipedia

Electronics Workbench

Pulse Width Modulation Wikipedia

Step 1: Circuit and Testing

The circuit i used is very simple with few parts but it works really well.
The fan will come to a complete stop with minimal buzzing.
I have made other speed controllers and they do not let the motor come to a complete stop and have a lot of interference ( buzzing ).

Step 2: Parts

1) 4093 Schmidt Trigger
1) 14 pin IC Socket
1) 1K resistor
1) 100K pot
1) #103 Cap
1) #104 Cap
1)1N4004 Diode.
1) IRF520 MosFet 
2) 1N4148 Diodes.

Perf board if you decide to build it on that.
I will use Photo Resist and etch a board.

Step 3: Eagle

I have loaded these screen shots as well as the Eagle files.
I have made the board so the pot can be either mounted on the board or remotely mounted
 In the case of remotely mounted just solder wires to the board that are long enough to attach the pot where ever it is mounted.  

Solder Pads 1, 2, 3 are for the Pot
Solder Pad 6 is +12V
Solder Pad 5 is Fan Pos
Solder Pad 7 is Circuit GND
Solder Pad 5 is GND OUT to the fan

This is not my design. I found it on line.

Step 4: Ghetto Exposure Box. PCB

Ghetto PCB is low budget. I do not have a fancie IR light box or even a poorly made light box.
I use a regular old CFB. Expose time 4 to 5 minutes.
There is a lot of ibles with exact procedures if you need more info.

Step 5: Populating the Board.

The 4093 needed to be in a socket. It could not take the heat of soldering.

Sorry i do not have any pics of the install and operations. My Web cam only goes so far from the pc with the USB cable. 
I am sure i have left out some important info, so ask if i didn't explian well.

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    9 years ago on Introduction

    Hi verence
    Thanks for the comment. I believe you are exactly correct. I over heated it i am sure and the solder wasn't flowing very well, longer time heating on the pin causing more heat.
    Lucky for me i had a spare 4093 at the time.


    9 years ago on Introduction

    Any chip can take the heat of soldering. That's how they are mounted in the industrial process. If they die while you are soldering them, you either take too much time to solder them or your soldering tool is far too hot. Other factors might be: the tip of your soldering iron is not clean or there is an oxide layer on the PCB or on the pins of the chip. Clean the PCB with fine steel wool (the pins of the chip as a last resort), make sure the tip is clean use a wet sponge or steel wool to get oxides layers of (be gentle, no grinding!). Soldering a 16 pin DIP should take about 10s. If you need longer, solder a few pins at a time and let it cool down in between.