Author Topic: How do you incorporate an LCD display into FX pedals/rackmounts?  (Read 2984 times)

KH602

How do you incorporate an LCD display into FX pedals/rackmounts?
« on: February 02, 2010, 07:46:28 PM »
Hi there, i am just wanting to find out more on how to get LCD displays to work with pedals

For e.g. turn volume, gain or tone, it will show either one on the display and show the value you have set it to by rotating the pot i.e. 1-100?

cheers

cloudscapes

Re: How do you incorporate an LCD display into FX pedals/rackmounts?
« Reply #1 on: February 02, 2010, 08:06:14 PM »
With a microcontroller.

Some of them are harder to use (parallel interface) but faster + more control + cheaper. Others are a bit more expensive but have an easy tx/rx UART interface.

http://www.sparkfun.com/commerce/categories.php?c=148

look at the serial enabled ones.

Whether you're going for parallel or serial, you'll still need a microcontroller. pics, avrs, whatever. Most micros have ADCs that can "intercept" a pot value, format it, add the text "Gain: " in front of it, do carriage returns, etc.

In a lot of cases, if you need a microcontroller to "intercept" pot values, it's because the micro itself is controlling the analog circuit as well. If not, then you need to "y-split" the potentiometer int oa usable 0-5 voltage range the micro's ADC can use.

if yo uwant to get into graphics, thats a lot more complex  ;D
http://www.youtube.com/watch?v=uBvK5JQ_6UA
~~~~~~~~~~~~~~~~~~~~~~
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potul

Re: How do you incorporate an LCD display into FX pedals/rackmounts?
« Reply #2 on: February 03, 2010, 01:49:24 AM »
In my microcontroller projects I use the cheap LCDs (compatible with the Hd44780), and I use the "2 wire interface" from Myke Predko.

http://www.rentron.com/Myke1.htm

This allows me control the LCD with just 2 I/O of the uC, and you just need to add another IC.
If you have enough free outputs in your uC, you can go directly.

Here you have a video of me testing an expression pedal and the LCD.

http://www.youtube.com/watch?v=9IN4ygZDnYI

And here the final product.

http://www.youtube.com/watch?v=vQyG3YAUAqg

Regards,

Potul

KH602

Re: How do you incorporate an LCD display into FX pedals/rackmounts?
« Reply #3 on: February 03, 2010, 11:56:14 AM »
cheers for the replys. Thanks for the videos, they are pretty neat. Cant fully understand what your saying but i understood most.

i like the idea of the pot being controlled and displaying on the LCD, i am wanting more than one pot to display on the LCD for like a 6 band EQ circuit i have. doesnt
have to be loads of graphics on the screen.

I am from the UK, so Rapid electronics will be the website am using if you can direct me with the things i will need.

thanks once again for your replies

potul

Re: How do you incorporate an LCD display into FX pedals/rackmounts?
« Reply #4 on: February 03, 2010, 12:32:10 PM »
Well, you will need at least:

-uC with 6 analog inputs and 2 free outputs
-A programmer for the uC
-A shift register or flipflop IC like the 74LS174
-Programming skills

By the way, I understand that you want  to monitor the pot position of an analog circuit... This can be tricky as it will depend on the circuit, what voltages you can monitor to use them as an input for the uC

The microcontroller simply reads voltages (usually from 0 to 5v), so you need to determine where in the circuit you can pick voltages that are linked with the pot positions. Not easy in an EQ, I think.
Another solution would be to use dual pots, so you can do both, control your EQ and send a voltage to the uC quite easily.

Regards