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Need help with my A Level project urgently!

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SkyPro

New Member
Hi everyone!

I would greatly appreciate some help which i need urgently.

I need to make something for my A Level project. All ideas seem to either have been taken by other people in the class or is too difficult.

I have decided after a lot hussle...to make a remote controlled fan. The speed of the fan will be controlled by remote control in three speed settings.

All I know is basically, it will transmit from the transmitter via Infra-Red. And there will be three buttons on the transmitter bread-board to control the power of the fan on the receiver side.

I have little Idea how it will work :( How do I code the infra-red as the receiver needs to know that its a different signal.
:cry:

Im not that good at this subject. :( All assisntance and ideas is very much appreicted.

Thanks in advance.

PS. I hate programming, so please try an suggest ideas that doesnt involve a microprocessor.

Thanks again.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
If you hate programming, you are in for a bad time!. By far the easiest way to do your assignment is to use a micro-controller, a PIC 16F628 would be fine for what you need - and my tutorials at http://www.winpicprog.co.uk include suitable IR remote control systems. For fan speed, it depends entirely on the sort of fan you are using, different fans require totally different speed control methods.
 

Russlk

New Member
Here is an analog way to do it: The transmitter will have a 555 oscillator with 3 timing caps. Each push button will insert a different cap to change the frequency. The receiver will have 3 PLLs to capture the frequency and activate the fan. 3 fets with different resistors can change the speed.
 

SkyPro

New Member
Thanks for the replies.
Especially Ruslk.

Ruslk: Can you please tell me what you mean by 'PLL'?

And 'caps' mean capacitors im assuming (Sorry, Im new here and not familiar with the abbrevations)

So Ruslk, you're saying, if the transmitter is transmitting at a ceratin frequency and the receiver can be made to pick up that frequency of infrared? How high of a frequency are we talking about here..If you can give me some rough idea.

Many many thanks for your help.
Regards.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
SkyPro said:
Can you please tell me what you mean by 'PLL'?

PLL is 'Phase Locked Loop', in this particular case a tone decoder, probably an NE567 - you would need one of these for each speed you required, tuned to a different frequency.

And 'caps' mean capacitors im assuming (Sorry, Im new here and not familiar with the abbrevations)

Yes, capacitors.

So Ruslk, you're saying, if the transmitter is transmitting at a ceratin frequency and the receiver can be made to pick up that frequency of infrared? How high of a frequency are we talking about here..If you can give me some rough idea.

The easiest way is to use an IR receiver IC (as used in TV etc.), these require a 38KHz modulation. You could then pulse the modulation on and off at the transmitter to provide a lower audio frequency modulation on top of the 38KHz. The output of the receiver IC would then be the original audio frequency, you feed that to the three PLL's which detect the tone and switch accordingly.

So the receiver is at least three IC's, plus the IR receiver, and the transmitter is probably two IC's (555's, or one 556). By comparison a micro-controller solution would require only a single IC at each end, and offer more speeds if required.

You've never mentioned what kind of fan it is, the simple resistor switching will only work with simple types. Presuming it's a commercial fan, with switched speeds already, it may be easiest to use relays to switch the existing contacts in the fan.
 

SkyPro

New Member
I would like to thank you all for you assistance.

Thanks very much Nigel Goodwood.

I am truly glad that I bumped into this site. And thanks to all the people who started these messege boards and to those who run it.

Nigel, I will need to ask a few more questions on what you have said, I hope you dont mind :) But that can wait till later.

Im in my electronics lesson right now and have spoken to my teacher, who have approved of the idea of my project. He has suggested that I start by building the motor. He wasnt happy about the idea of using 3 fets with different resistors to change the speed of the motor as suggested by Russlk. He said its very inefficient and a more appropriate way to control its speed would be to use pulse width modulation. I am now going to research a bit about how I can use this method of control. Again I would appreciate any help you could give on this.


Regards.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
SkyPro said:
I would like to thank you all for you assistance.

Thanks very much Nigel Goodwood.

Who's that? 8)

Im in my electronics lesson right now and have spoken to my teacher, who have approved of the idea of my project. He has suggested that I start by building the motor. He wasnt happy about the idea of using 3 fets with different resistors to change the speed of the motor as suggested by Russlk. He said its very inefficient and a more appropriate way to control its speed would be to use pulse width modulation. I am now going to research a bit about how I can use this method of control. Again I would appreciate any help you could give on this.

Yes it would be very inefficient, but it was only a suggestion to keep it simple for you - I'm sure Russlk wouldn't do it that way himself.

Requiring PWM makes a PIC even more advantageous - the PIC 16F628 has an inbuilt hardware 10bit PWM stage - perfect for speed controlling a DC motor for your fan!.
 

jem

Member
If you are using a DC motor fan, then you can also take a look at the NJL21H from NJR (www.njr.com). You can then have quite a wide range of speed by using the output of the receiver as a PWM signal.

For the Tx, a couple of 555 astables should do. One if for the basic 38KHz carrier, and the second one to PWM (more like OOK) the carrier.
 

SkyPro

New Member
Hi, thanks again.

I have built the PWM circuitry yesterday and its working :D

I have generated the triangle waves required at the negative input (if i recall correctly) with a signal generator. I need to know how I can build my own triangle wave signal generator. Anybody can direct me somewhere where I can see a circuit diagram? Or can kindly post one here :) I hear its simple from my teacher but he said nothing more :roll:

Thanks :)
 
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