Electronics > Beginners
555 Motor Speed Controller
Zero999:
--- Quote from: m3vuv on December 21, 2019, 09:37:09 pm ---for the non plarised caps,cant you use 2 polaried ones back to back?
--- End quote ---
Why would you want to do that? The non-polarised capacitors are all small, ≤100nF and are difficult to find in polarised versions and non of the capacitors in the schematic need to be non-polarised.
mike_mike:
I also made a simulation in LTSpice for this schematic.
Please have a look...
The frequency with C4=470pF is about 50KHz, and with C4=1nF, F=24KHz. Which is the correct frequency for the DC fan motor (120 mm fan) ?
I checked the physical circuit, and it does not work with the 120mm fan. The fan does not spin. I also checked with 2 80mm fans, one by one, and it is working. Do I need a particular type of 120mm fan ?
The 120mm fan is rated at 12V and 0.16A (DC brushless fan). I don't know the current rating for the 80mm fan, all I know is that it is rated at 12V.
Zero999:
--- Quote from: mike_mike on December 22, 2019, 01:53:50 pm ---I also made a simulation in LTSpice for this schematic.
Please have a look...
--- End quote ---
Some of those symbols aren't included in the default install.
The problem is there's no way of embedding models into LTSpice schematics. The only way to upload them for everyone to view is to put all the symbols into a zip, but some of the more security conscious will avoid opening zips from unknown sources because they can contain anything.
An alternative is to stick to standard symbols. The potentiometer can be modelled as two resistors in seires, with the wiper being the tap. Changing the resistor values alters the wiper position. This can be a fiddle so I've used variables wpr which is the wiper can range from near zero to near one (it can't equal 0 or 1 because LTSpice doesn't support zero Ohm resistors) and res which is the total value of the potentiometer,
See my potentiometer tutorial for more information.
https://www.eevblog.com/forum/beginners/simulating-potentiometers-using-ltspice/msg2358510/#msg2358510
--- Quote ---The frequency with C4=470pF is about 50KHz, and with C4=1nF, F=24KHz. Which is the correct frequency for the DC fan motor (120 mm fan) ?
I checked the physical circuit, and it does not work with the 120mm fan. The fan does not spin. I also checked with 2 80mm fans, one by one, and it is working. Do I need a particular type of 120mm fan ?
The 120mm fan is rated at 12V and 0.16A (DC brushless fan). I don't know the current rating for the 80mm fan, all I know is that it is rated at 12V.
--- End quote ---
DC brushless fans are often incomputable with PWM. You could try reducing the frequency to the kHz or even 200Hz range and see if that works. The down side will be audible noise and even then, there's no guarantee it'll work.
not1xor1:
--- Quote from: mike_mike on December 22, 2019, 01:53:50 pm ---I also made a simulation in LTSpice for this schematic.
Please have a look...
The frequency with C4=470pF is about 50KHz, and with C4=1nF, F=24KHz. Which is the correct frequency for the DC fan motor (120 mm fan) ?
I checked the physical circuit, and it does not work with the 120mm fan. The fan does not spin. I also checked with 2 80mm fans, one by one, and it is working. Do I need a particular type of 120mm fan ?
The 120mm fan is rated at 12V and 0.16A (DC brushless fan). I don't know the current rating for the 80mm fan, all I know is that it is rated at 12V.
--- End quote ---
as far as I can remember (it looks like I did not save any note on my PC) the circuit I built on a breadboard a few years ago worked correctly only at a very low frequency... in the order of 100 Hz (I think I used a 2 wires fan)
BTW there is no need for a mosfet driver, you could just use a BJT (e.g. BD 136/137)... PC fan are low power and the frequency is low
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