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The Digispark => Digispark Projects => Topic started by: cboden on December 26, 2013, 04:51:03 am

Title: 64 channel modular control system
Post by: cboden on December 26, 2013, 04:51:03 am

I was asked to built a control system that could switch up to 64 channels on a model railroad to iluminate the houses. To make the effect as realistic as possible, the channels should be switch on and off by a randomized function.

I decided to implement this by with a Digispark. I really love the result of this project and decide to share it here with you ... maybe you can get some inspirations from it.

To make live easier I decided to put the Digispark on a new breakout board with 4 I/O pins and an I2C bus.
(http://cboden.de/images/LightComp/CPU_klein.jpg)

Then I designed an interface board with a PCF8574 on it to expand the I/O ports. I want to make it as easy as possible to configure the base address for it and used pull down resistors and a DIP switch for the high level on the configuration pins. I also added a second I2C connector to make it simple to connect another interface (or any other I2C device) The board also contains a ULN2803 to boost the 8 channels of the expander. This darlington driver array can provide up to 500 mA. This is more then I could take from the Digispark and so I added a 7805 to the board for its own power supply.
(http://cboden.de/images/LightComp/Interface-Treiber%20klein.jpg)
The 8 channels are routed to two terminal strips. The output of 5 V is of course to much for a LED and so I designed a adapter board with some resistors on it.
(http://cboden.de/images/LightComp/WiderstandsInterfaceKlein.jpg)
The stackable headers of that board can be put into the terminal strips of the interface board.
(http://cboden.de/images/LightComp/Treiber%20mit%20Widerstands-Interface%20klein.jpg)
The big advantage of this approach is that this resistor board can be replaced by an relais board for example
(http://cboden.de/images/LightComp/relais2.jpg)
I'm currently working on a 8 channel MOSFET shield to extend the flexibility of that system.

Please let me know your thoughts on that project.

Title: Re: 64 channel modular control system
Post by: Mark on January 03, 2014, 02:17:02 am

cboden
A very well thought out project.

This probably has various other uses as well.
Thanks for sharing

Mark