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8
Relay Driver Board
This
relay board is a replacement for the one I am currently using to drive my irrigation
systems. The main reason for this project is I now have new things to control
as well as the six water valves. This at the moment is the LED front garden
lighting. I also have a back EMF problem when I turn off the front lights causing
me some problems. Anyways, the answer is a completely opto isolated 8 relay
driver board. I have been asked to make it compatible with both HV
and Comfort output ports which
means I am having to do some thinking ;-(.
The last update I hope
The printed
circuit boards arrived as promised and wow, they are beautifully crafted. I
have assembled the first one and had it working from both HV and a small PIC
micro controller within an hour or so. Below are the pictures of the almost
bare board and the first completed unit.
I am
waiting on the first shipment of parts and then I will then complete the LED
feedback board and get some pictures of that here as well.
Click
for a larger image 100k
Click for a larger image 96k
Now I
have completed this stage of the project these units are up for grabs.
Please see the for sale
page for more information.
Update 6
I have
now ordered the printed circuit boards and am waiting on delivery. I am hoping
they should be here in the next week or so. So, assuming I have not dropped
a big clanger the first boards will be ready pretty soon. Pictures and story
to follow as soon as they have been built and tested.
Update 5
After extensive testing of the mark one board
we have found the relays a little lacking in controlling some of the loads that
are planned for them. In short the answer was to adopt a new relay and redesign
the board around them. I have now done this and after many late nights this
is what I have come up with.
Click for larger image - 140k
Click for larger image - 52k
The new specifications now go something like
this.
On
the controller side of the board
Ø
Power supply is by 5 to 15 volts DC only
Ø
The opto-isolation chips have built in diodes
for back EMF protection. They are available without but the price difference
is minimal so I have gone for the ‘better’ chips.
Ø
The chips are powered by the controller or
another source and activated by grounding the appropriate wire. If a micro controller
is used there is both +ve and ground so only one power supply would be needed
for both. All in the interest of neatness!
Ø
Connection is by IDC connector plug. The socket
is provided with flying leads for the relays and separate +ve and ground via
screw terminals.
On
the relay side of the board
Ø
Power supply is by 9 to 30 volts AC or DC
Ø
8 relays rated at 1 amp at 24 volts DC and
½ amp at 100v AC each. The maximum switching power is 24 watts. Coils are 5
volts which is derived from the power supply.
Ø
Power can be provided from the supply to the
common connector on the relay. This then passes through the fuses and is optional
via a switch.
Ø
A ½ amp thermal fuse protects each output
when power is supplied from the board. The trip current is 1 amp.
Ø
There are three connectors per relay Common,
Normally Open (NO) and Normally Closed (NC). If power is from the board the
common is not connected. If it is not though then the common terminal is connected
to the common on the relay. This enables all sorts of other dry contact switching
or even the supply of a different voltage. Note though that this type of input
is not fuse protected.
Ø
The outputs use the type of connector that
plugs onto a post. These can be removed from the board without removing the
wiring.
Ø
4 mounting holes are provided which fit the
Comfort mounting system
(I hope).
See
the design here in PDF format.
And
now the complete layout here, again in PDF.
And here is the bill
of materials
===========================================================================
All from here is out of date
===========================================================================
Update 1
Well,
true to form the first board rolled out of the etching tank and into solder
mode and, when tested did NOTHING……… Bummer. After two minutes looking at it
I realised where I had gone wrong. Half the input side was wired to be triggered
by a current from the controller and what should have been the ground was +ve.
Two lots of positive = no current flow. Some hasty work with a wire and a bit
of solder and it worked as designed. The only slight snag was I meant to design
it to be triggered by providing a ground for the opto coupler not the other
way round. This was not something I could bodge with a bit of wire and solder
(easily anyway) so a quick redesign and out to make another board.
Two hours
later and I now finally have a working board in my hands. I have to get some
more parts for it but it tests out well so far so fingers crossed. As soon as
all the parts are here I will update these pages with pictures etc.
With
all relays on however it draws about 60 milli amps for the opto chips plus the
power LED. This latter is about 25ma at a guess.
As for
cost, it looks as though a fully populated board will cost around 25 pounds
+ the PCB. This is a guesstimate though as I have not done the maths properly
yet. One PCB is about two hours work + the board cost so not very cheap I’m
afraid. On the plus side though a micro controller (e.g. PIC) can easily control
this board (and that might even turn into another project sometime, you never
know).
Update 2
Well,
parts arrived from Rapid Electronics in usual rapid time (;-)). It only took
about 10 minutes to solder on the remaining components and I now have a fully
functioning board ready for some extensive testing.
In the
mean time here is the promised picture.
Click for larger image -
97k
If you
think of the blue wires as being on the left side then there are two power connectors
on the top corners along with green indicator LED's. The left one is for the
controller and the right one for the relays. The two chips on the left side
are the opto isolators with the red line being the resistor network to stop
the chips burning out. All this kit is isolated from the rest of the board.
To operate the relays the blue wires need grounding to the same ground as the
top left power connector. This power connector is probably connected to power
out from either HV or Comfort.
The relays
are all lined up down the middle and the brown disks are the thermal fuses.
Finally the red LED’s are ‘downstream’ of the fuses to indicate whether there
is power or not when the relay is on. The large screw type connector block is
removable so no unscrewing of wires if the unit needs disconnecting for any
reason. Finally the chip on the bottom right is the resistor network for the
LED’s. Voila, there you have it.
This is the above board in a Comfort
enclosure. Click for larger image - 80k
I am
now going to look at the possibility of having these PCB's made professionally.
We shall see.
Update 3
Well,
in the tradition of all things I seem to build I am now on the mark 3 version.
Steve Cooper popped down for the evening and we did some serious testing and
found that that any loads with a capacitor fitted e.g. electronics etc. would
not switch off. In my case it was a blind turner and it was very frustrating.
Other items e.g. water valves operated perfectly. We are still not quite sure
what exactly was happening but it had something to do with reverse current hence
the capacitor theory. The fact that I use the same +ve to feed both the coil
and the switched current had something to do with it but my electronics is not
quite that good yet. The solution is easy though and a diode soldered in series
solved it instantly.
The board
has now been through another re-design and has now sprouted diodes on all the
outputs. These are jumper by-passable so the owner has the choice of whether
they are used or not. The main reason for this is there is approximately a .6
volt drop associated with diodes which folks may not want.
There
has been another useful feature added and that is the relays have been split
into two lots of 4 at the power supply (thanks Frank McA for the suggestion).
This means there is now another power supply connector (total 3) of which two
of these are for the relays and can use different voltages. If only one supply
is wanted these can be connected together by jumper and all 8 relays run off
one this one supply.
Steve
also brought up some Comfort boards of both sizes he had and the relay board
will now fit into the Comfort enclosure.
Finally
there is an extra ground connector in case the power for the switching circuit
is supplied by something other than the circuit grounding the trigger wires.
Here
are the updated copper and silk screen views. Don’t try and print the copper
view for production at home as PDF documents are slightly out of scale which
would be a problem.
The documents
have been removed as they are now out of date.
Full current specifications go something
like this:
On
the controller side of the board
Ø
8 opto-isolated relays rated at 1/2 amp each.
Ø
The opto-isolation chips have built in diodes
for back EMF protection. They are available without but the price difference
is minimal so I have gone for the ‘better’ chips.
Ø
The chips are powered by the controller or
another source and activated by grounding the appropriate wire. If a separate
power source is used a ground connection is provided. If a micro controller
is used there is both +ve and ground so only one power supply would be needed
for both. All in the interest of neatness!
Ø
Connection is by IDC connector plug. The socket
is provided with flying leads for the relays and separate +ve and ground.
On
the relay side of the board
Ø
8 DIL relays rated at 1/2 amp each and mounted
in sockets for easy replacement. Thes are rated at up 100v DC for the switched
current. Coils are 5 to 16 volts.
Ø
Each output is protected by a ½ amp thermal
fuse. The trip current is 1 amp.
Ø
Reverse current protection is provided by
a diode which is optional and can be switched out by a jumper.
Ø
Each output has a red (or your choice between
red and green) LED for state monitoring. If the fuse trips this goes out.
Ø
The relays are in two banks of 4 for powering.
Power can be from two different supplies at different voltages. The
two sides can be connected together if only one supply is used.
Ø
Power to all three power sockets is shown
with a green LED (or your choice between red and green).
Ø
The outputs will use the type of connector
that plugs onto a post. These can be removed from the board without removing
the wiring.
Ø
4 mounting holes are provided which fit the
Comfort mounting system.
That’s
about it for the time being. More testing and another prototype to do/build
and then we should be ready to actually have some of these made. Here's hoping.
Update 4
I have now built the final prototype
and I was very pleased when it worked first time. There is nothing new to add
really apart from some pictures so here they are:
This is the top of the board (click
for larger 104k image)
This the bottom (click for larger
111k image)
And finally this is an angled
shot showing it is not very high at all (click for larger 97k image).
I am now working on getting the Gerber
output correct for production.
This page last updated on 9th September 2002