Author Topic: 555 Motor Speed Controller  (Read 4637 times)

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Offline Zero999

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Re: 555 Motor Speed Controller
« Reply #25 on: April 24, 2019, 02:44:14 pm »
Waveforms looks good. I would recommend to put a snubber in parallel with load and use of UF4007 diode instead of 1N4007. Reason for it is voltage spikes on load and MOSFET. This voltage spikes are high (double of power supply voltage) and can hurm MOSFET if higher currents and voltages are used. With snubber you can reduce voltage spikes.
What is snubber and how to dimension it is discraibed in this pdf https://www.illinoiscapacitor.com/pdf/Papers/RC_snubber.pdf
Snubber is RC circuit connected in paralled with inductive load and purpose of it is to reduce voltage spikes caused by fast switching of mosfet (or any other switch).

No, R7 is not needed. Output of NE555 is also totem pole configuration (there are two transistors, one switch to positive power supply input and other to negative power supply side (gnd)) but it can deliver max +/- 0.25A. With external totem pole you can achive higher currents (like +/-0.5A) that are useful for fast switching of MOSFET.

Nice work  :-+
Using a faster diode such as the UF4007 is a good idea.

No snubber is required, because the freewheeling diode short circuits any back-EMF pulses.

In this case, a snubber would just dissipate power and reduce the efficiency of the circuit.

The downside with having an external emitter follower is it reduced the voltage swing of the 555 timer. R7 isn't needed, but it may turn off faster with it.
« Last Edit: April 24, 2019, 03:48:44 pm by Zero999 »
 
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Online iMo

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Re: 555 Motor Speed Controller
« Reply #26 on: April 26, 2019, 09:37:18 am »
TV310G is 150ns max recovery time and 15pF and UF4007 is 75ns and 17pF. Otherwise both are the similar spec.
I would use the TVR10G in your app when the diode in my junkbox..
PS: answered a Q which has disappeared already.. :)
« Last Edit: April 26, 2019, 09:40:34 am by imo »
Readers discretion is advised..
 
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Offline mike_mikeTopic starter

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Re: 555 Motor Speed Controller
« Reply #27 on: April 26, 2019, 09:51:03 am »
PS: answered a Q which has disappeared already.. :)
Yes, I deleted the message because I think that I could find a better diode for this project, if I will search in some old equipment...
 
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Offline mike_mikeTopic starter

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Re: 555 Motor Speed Controller
« Reply #28 on: April 26, 2019, 12:16:54 pm »
I found RG10 diode in that old TV.
I checked the Datasheet and it says that the trr is 50ns and 100ns for RG10 and 75ns for UF4007.
In this situation, it is safe to use RG10 as replacement for UF4007 ?
 

Online iMo

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Re: 555 Motor Speed Controller
« Reply #29 on: April 26, 2019, 12:22:54 pm »
I think yes. RG10 is 400V/1A and fast enough imho.
Readers discretion is advised..
 
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Offline mike_mikeTopic starter

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Re: 555 Motor Speed Controller
« Reply #30 on: April 26, 2019, 02:39:31 pm »
 I tried the attached schematic with RG10 diode and a mini drill (a similar mini drill to Proxxon), and I got the following results:
a. On the mini drill terminals: DS0000.jpg
b. On pin 3 of 555: DS0003.jpg
c. On the G of IRF630: DS0004.jpg

Please have a look at the results and tell me if they are good ?
 

Online iMo

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Re: 555 Motor Speed Controller
« Reply #31 on: April 26, 2019, 02:47:45 pm »
50kHz PWM - isn't that too high?
Readers discretion is advised..
 

Offline mike_mikeTopic starter

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Re: 555 Motor Speed Controller
« Reply #32 on: April 26, 2019, 03:21:24 pm »
Initially the frequency was about 160KHz.
I reduced it to around 40KHz, because I was told to do that...

If I will reduce again the frequency, there could appear some audible noise from the motor ?

When the frequency was lower (with another circuit with 555) then I could hear a noise from the motor at low speed...
« Last Edit: April 26, 2019, 03:23:15 pm by mike_mike »
 

Offline mike_mikeTopic starter

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Re: 555 Motor Speed Controller
« Reply #33 on: December 21, 2019, 02:03:38 pm »
Hello, I am interested in building a fan controller for my PC using the schematic discussed in this topic.
Do you have any suggestions ?
Are there any other things that should be added to this schematic ?
 

Offline m3vuv

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Re: 555 Motor Speed Controller
« Reply #34 on: December 21, 2019, 09:37:09 pm »
for the non plarised caps,cant you use 2 polaried ones back to back?
 

Offline Zero999

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Re: 555 Motor Speed Controller
« Reply #35 on: December 21, 2019, 10:49:53 pm »
for the non plarised caps,cant you use 2 polaried ones back to back?
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.
 

Offline mike_mikeTopic starter

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Re: 555 Motor Speed Controller
« Reply #36 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.
« Last Edit: December 22, 2019, 09:09:34 pm by mike_mike »
 

Offline Zero999

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Re: 555 Motor Speed Controller
« Reply #37 on: December 22, 2019, 10:49:12 pm »
I also made a simulation in LTSpice for this schematic.
Please have a look...
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.
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.
 

Offline not1xor1

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Re: 555 Motor Speed Controller
« Reply #38 on: December 23, 2019, 06:29:14 am »
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.

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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