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#52368 High power multiplexing help

Posted by mcinnes01 on 26 August 2013 - 03:59 PM in General Discussion

Hi,

 

I am just in the process of rewiring my house using a radial system or in fact 2 seperate radial systems (one for the basement/ground floor and one for the first floor/loft). By radial system I mean each socket and light goes back to the distribution board.

 

The idea is that I can control each socket or light separately and so each of these will terminate on its own solid state 25 amp relay that will be din rail mounted in the distribution board. Each light switch will run on a low power system using cat5 cabling and so all the switching will be done using solid state relays. This not only allows me to manually control the lights using manual switches, a 24v din mounted power supply and CAT5 cable to the relays. But it also allows me to centralised control that I can interface with via the netduino. The reason for this is that you must ensure that there is a switchable light per room and it acts as a backup in case I have a software or electronics issues, most importantly this also avoids the Mrs getting annoyed if she can't switch the light on etc. ;)

 

What I am trying to do is create some din rail mounted modules that will provide the switching control for the relays. Each module will use CAT5 connections to connect it back to a central module that will house the netduino and will split the SPI which will be used to multiplex the control logic and distribute the switching voltage from the 24v 3.2A 85W din mounted power supply.

 

Each module will switch 8x 25amp relays using 24v, will have 8 LEDs to indicate what is on, will contain a 74HC595 shift register, a 74HC245N CMOS and a ULN2803 transitor array, plus some resistors or resitor array.

 

The relays have approximately a 2.5v 30ma voltage and current drop respectively.

 

The 4 twisted pairs in the CAT5 will carry the 3 connections for the SPI, 1 connection to return QH from the 595s so they can be daisy chained, common Gnd, 3.3v and 24v.

 

What I need a little help with is as follows:

  • Am I missing any connections on the 74HC245Ns, there is a direction pin (pin 1) and a QE pin (pin 19). I am not sure what to do with these?
  • Can you see any errors in the circuit or see any problems that it might face, and can you offer any solutions if so?
  • As I will have a fair few of these boards and each will have 8 small 3mm leds 30ma 2.5v, would I be better moving the leds to the 24v side of the circuit and if so what will I have to change? Would I need any extra resistors, diodes, caps etc?
  • The resistors I haven't even calculated and this is something I am terrible at, if I leave the LEDs where they are now what resistors would I need? I was thinking of using a resisor array from my inspiration for the circuit (see below). However linked to the previous question what if I moved the LEDs up to the 24v circuit so they aren't running off the netduinos power? Posted Image
  • Would the circuit benefit from any caps to level things out and if so what size and where?
  • Final question do I need any additional protection diodes for the netduino or chips?

Here is a fritzing (see Din Mount Relay_bb.jpg) of what I was thinking for the Din Modules and there is also the netduino shield which distributes the 24v and SPI (see Din Shield_bb), any help moving the LEDs to the 24v side would be much appreciated!

 

As a key:

Red = 24v

Black = 3.3v (from netduino)

Green = Common Gnd

Orange = Returned QH

White = MOSI

Purple = SCLK

Yellow = SS

 

Andy

Attached Thumbnails

  • Din Mount Relay_bb.jpg
  • Din Shield_bb.jpg



#52329 Netduino Go Future

Posted by mcinnes01 on 24 August 2013 - 08:41 PM in Netduino Go

Is there any road map for go! bus 1.5 to be available in some form that will allow things like the ethernet module and multi shield base support, to come out before Christmas this year?

 

I'm fully automating my house in the next month and it would be great to have Go! as the core, using either ethernet or wifi on a shield base (serial), plus multiple shield bases for extra SPI, Serial etc etc and maybe since the plus 2 has it....the long waited 1-Wire support?

 

Andy




#52328 New book: Netduino Home Automation Projects

Posted by mcinnes01 on 24 August 2013 - 08:21 PM in General Discussion

Ordered! Can't wait I am just starting a major home automation project so this could be useful, although my spark is quoting £11K for the infrastructure I want putting in place :o




#52130 N+2 communication with WebApi

Posted by mcinnes01 on 13 August 2013 - 07:21 PM in Project Showcase

I would love to see your code including the web api? Are you using signalR to update your page?




#52128 Netduino Go Future

Posted by mcinnes01 on 13 August 2013 - 06:59 PM in Netduino Go

Cheers Mark!

 

It looks interesting, but sadly this will take the spi up on the shield base which I use for other things and with the lack of multi shield support this doesn't leave much scope ;)

 

#Subtext# I was also trying to provoke some interest from Chris and maybe a response?

 

#Off Topic# How was Manchester mini maker faire and where did you hear about it? I missed hearing about it till too late :(

 

Andy




#52106 Netduino Go Future

Posted by mcinnes01 on 12 August 2013 - 09:45 PM in Netduino Go

Maybe a bluetooth module would inject the much needed interest back in to the netduino Go! project, by allowing it to piggyback off the energy that has been put in to Agent? It would drive interest both ways from people who have an Agent watch wanting to control hardware and people who control hardware wanting another interface device by using the Agent smart watch. I understand secret labs are working hard to make sure they deliver their more commercial product, Agent, for Christmas to all of us backers. Does this mean once the watch is up and the production line running, some energy will go back in to the Go! line? I really hope so, I can't wait to do something useful with my Go! :)

 

Andy




#52089 Netduino Go Future

Posted by mcinnes01 on 11 August 2013 - 02:41 PM in Netduino Go

Hi Chris,

 

What needs to happen to get things like SD shields that use SPI and things like serial wifi modules to work with the shield base? Are these planned for the next release?

 

Are there going to be any interfaces for AGENT to work with GO!?

 

Cheers,

 

Andy





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