The total cost for this DIY job came out to be just Rs 90!
Bhpian chhanda das recently shared this with other enthusiasts:
Earlier this year, after an unfortunate incident of tea spillage, the 12-volt 2-ampere rated pulse width modulation (PWM) based motor speed controller died which was not a major problem or so we thought. These controllers cost around ₹ 45-50 per piece. My son went to the market and bought a replacement controller of the same specifications as the earlier one. It lasted for around a month before it died. Must have been from a bad batch.
My son then replaced the controller again and the motor too, for good measure. This time, the controller lasted for a week before going kaput. At one point, he replaced the wiring and the connectors too. This went on three more times. At the end, we came to the inevitable conclusion that the quality of the controller was compromised. And replacing their individual components didn’t seem feasible for us because of their small size. Hence, my son decided to make a motor speed controller for the 555 motor himself.
DIY Motor Speed Controller
Components used :
- A 40x40x10 millimetre (mm) or 4010 model 12 volt (v) fan was used. Instead, a smaller 30x30x10 mm or 3010 model 12V can also be used but that is difficult to find and more expensive.
- A 2×3-inch single-sided copper-plated perforated (perf) board or zero printed circuit board (PCB) was used.
- One set (10 wires) of male-to-male jumper wires for breadboard connections. These wires are rated to handle around 1 ampere of current each.
- A large aluminium heat sink with a suitable nut and bolt for the TO-220 packaging standard of PCB components.
- A 25V 470 micro Farad radial through-hole aluminum electrolyte capacitor was used but a similar 16V capacitor would have worked fine for our 12V 555 motor.
- Heat sink compound which is also known as thermal compound.
- One IRFZ44 n-channel metal-oxide-semiconductor field-effect transistor (MOSFET) in the TO-220 package.
- A 3-terminal 5 kilo-ohms single-turn rotary linear potentiometer with a plastic shaft and knob.
- A 4-pin screw PCB terminal block with 5 mm pitch spacing
- A 40-pin 2.54 mm pitch male breakaway pin header or Berg strip.
- Zip ties
Connections :
A 25-watt soldering iron and lead-free soldering wire were used for the connections. A screwdriver and a plier were used for the nut and bolt. For reference, here is the terminal/pin nomenclature for the IRFZ44N MOSFET and the 5-kilo-ohm potentiometer.
1) The first step would be to apply the thermal compound to the back of the IRFZ44N MOSFET and fit it to the heat sink by using the nut and bolt.
2) Then the 3 potentiometer terminals need to be soldered onto 3 individual pins broken from the Berg strip.
3) The next step would be to arrange all the components on the non-copper-plated side of the perf board as can be seen in the image below.
4) Now a solder track needs to be created on the copper-plated side of the perf board in such a way that the ground terminal of the potentiometer, the negative terminal of the capacitor, the negative input terminal of the supply and the negative output terminal for the 555 motor are all connected together. If you face any difficulty in routing the solder track, then you can use the jumper wires. Please note that you have to use two wires in parallel per terminal since the wires are rated at 1 ampere each and the 555 motor is rated for 1.8 amperes.
5) Another solder track needs to be created on the copper-plated side of the perf board between the input terminal of the potentiometer and the gate terminal of the MOSFET.
6) A third solder track needs to be created on the copper-plated side of the perf board in such a way that the power terminal of the potentiometer, the drain terminal of the MOSFET and the positive input terminal of the supply are all connected together. If you face any difficulty in routing the solder track, then you can use the jumper wires. Please note that you have to use two wires in parallel per terminal as earlier. It would be pertinent to note that if you want to add reverse polarity protection, then you can add one set of 3 x 1N4007S diodes joined in parallel between the positive input supply terminal and the rest of the components on this solder track in series. My son chose to avoid the diodes to avoid the inevitable voltage drop across them.
7) Finally, a fourth solder track needs to be created on the copper-plated side of the perf board in such a way that the positive terminal of the capacitor, the source terminal of the MOSFET and the positive output terminal for the 555 motor are all connected together. If you face any difficulty in routing the solder track then you can use the jumper wires. Please note that you have to use two wires in parallel per terminal as earlier. After all the soldering is completed, it should look something like what can be seen in the image below.
8) The last thing to do is to connect the 4010 fan to the 555 motor in parallel and that can be done at the PCB terminal block itself.
And the motor speed controller is ready for use. The total cost came to ₹90.
Here is a short demonstration video.
If you want to replicate this, then please do so solely at your own risk.
Wishing you all happy and safe drives ahead!
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