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Newbie needs circuit reviewed...please!!!!! :)

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New Member
Hello all,

First of all I would like to introduce myself since I haven't posted here before but have been roaming this forum for a while now.

Ok, enough with that onto my reason for being here.

I am a newbie with respect to circuit design and have decided to do as I always do and jump into the learning process with a difficult project. The project is a multi-channel, multi-voltage fan controller for my PC. The controller will employ the use of 4 NC momentary switches, 2 for channel selection and 2 for voltage selection, that when pressed will either increment or decrement the Channel or Voltage setting depending upon the buttons pressed. The display for this controller will consist of Bargraphs displaying the voltage level and a single 3mm LED to identify the channel being controlled.

I have started on the circuit for channel and voltage selection and need someone to review what I have so far and tell me what I am missing or if I am even approaching this the most effective way. Here is the Button control circuit as it sits now.

Thanks in advance for any help.



I took a look at your circuit. I would suggest you rethink your approach. I would suggest looking into using a microcontroller as your brains. You could easily write some software to multiplex your displays and read the buttons. You might also be able to generate a high frequency PWM system to control the fan motor speed. The micro approach would greatly reduce the parts count and afford you some flexibility in that you can change the software easily. Also, most modern micros can directly drive the LED display.


New Member

thanks for the comments. I like the idea of using a microcontroller from many point the most noteable being the ability to have the microcontroller display the voltages and mode selection to an LCD. However, the added time to learn both circuit design and microcontroller programming and interfacing is a little over my head. Given this I would like to stay with something that although isn't as efficient or flexible but will work and will allow me to learn about the basics of circuit development. Does this make sense?

Let me ask the following questions:

1. Have I missed something in the circuit other than the voltage setting and display portion?
2. Would the design provide the control functionality that I am looking for?
3. Is my selection of IC's appropriate for the design?

Thanks again for the help in advance.



New Member
From taking a quick look at your schematic it appears the 74192 up/down counters will suffer from contact bounce. The pushbuttons need a conditioning circuit . Do a search for contact bounce suppression circuits.
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