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My DIY Digital Preamp/Source Selector w/ LCD & Remote
My DIY Digital Preamp/Source Selector w/ LCD & Remote
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Old 30th October 2005, 08:07 AM   #1
Mr.Radar is offline Mr.Radar  United States
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Join Date: Jun 2005
Location: Minnesota, USA
Default My DIY Digital Preamp/Source Selector w/ LCD & Remote

This is a bit more brief than my first version of this post because my browser crashed while I was editing it.

Design here.

This was surprisingly easy to design, especially considering that I haven't ever done anything with electronics before (though I expect laying it out when I build it will be a bit harder). It was probably so easy because this is really just an amalgamation of a bunch of other designs.

At the heart of this design are two PIC18F252 microcontrollers. One handles the LCD, Volume and Balance controls, the source selection relays, and the volume control IC. The second PIC18F252 handles the IR receiver and front panel switches.

I haven't written the code to control the microcontrollers, but I have it planned out enough that I shouldn't have any major problems writing the code.

The LCD is a 24x2 backlit display based on the Samsung S6A0069 chip (which is a clone of the widely-used Hitachi 44780) (digikey # 67-1775-ND).

The IR receiver is a Sharp GP1UW700QS (digikey #425-1856-ND) IR receiver/36KHz demodulator. I haven't decided on which device to use the codes from for the remote control, but it'll definately be based on the RC5 protocol since that's easier to interpret than most others.

The relays are all G6H-2-DC5 from Omron Electronics Inc-ECB Div (Digikey # Z740-ND).

All the pots are 5K linear taper and all of the switches are Off-Mom push button switches (except the power switch (not shown) which is an Off-On rocker swicth).

I originally planned to add tone controls to this preamp but to keep costs down and simplify the design I've had to leave them out so just ignore the relevant section on the schematic (I won't be programming for it, unless everyone would really like me to).

The power supply (not shown) is a pretty standard design based on the LM317/337 regs. (Does anyone know where I can buy a 1.5+A@18v (with the secondaries wired in parallel) toroidal transformer (115v primary voltage) at a reasonable cost?).

Anyways, I'm going sleep now. See'ya in the morning.
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Old 8th February 2006, 07:17 AM   #2
hes21 is offline hes21  Australia
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Join Date: Dec 2005
Location: Australia
How is it progressing?

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Old 8th February 2006, 11:07 AM   #3
reever is offline reever  United States
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Join Date: Mar 2005
Location: Laurel Springs N.J. (Near Philly)
How much more cost would be involved if tone controls were added????
Of course there are those who would not want or even consider such a thing, but I'm willing to bet there are many who would genuinely appreciate such an endevour......

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Old 8th February 2006, 11:26 AM   #4
jackinnj is offline jackinnj  United States
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Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
My DIY Digital Preamp/Source Selector w/ LCD & Remote
well, now that you've wired everything together -- here's a product which could have saved you some time and space. I have used in 3 projects -- the LCD+ from basicx www.basicx.com -- the unit shown is the LCD+2 -- which is $69. it has a ULN2803A relay driver, 8 port 10-bit ADC, two serial ports, adjustable contrast and brightness, user defined characters etc. -- you can see the Atmel processor -- I went from using discrete LCD's to these units since it combined a lot of functionality for a really great price. The 4x4 keypad interface is very, very helpful in an application such as yours.
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