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Wednesday, 03 October 2012 16:26

8 Channel Relay Box

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This is a 8 channel relay box that the input connect to a controller allow it to control large loads like home appliances.
 
I'm using this relay box for a snooker centre to control snooker table lamps. The lamps consists of 6 pieces 20W and 3 pieces 10W fluorescent lamps, total of power consumption is 150W per table. Picture below shows the snooker table lights for the snooker centre.
 
 
 
 
Snooker CenterSnooker Center 
  
As shown in figure below, the Omron DC12V DPDT Relay (MKS2P) is using in this projects. According to the specification, the relay can handle 10A for 250V AC or 5A for 30V DC.
 
OMRON MKS2P RelayOMRON MKS2P Relay
The max power (P=IV, P=10A x 250V) for the relay is about 250W per contact which is more than enough to handle 150W snooker table lamp. For this project, the relay contact is connecting in paralle in order to handle higher power in the future.
Relay contact in ParalleRelay contact in Paralle
In parallel configuration all relays contacts will close at the "same time" (I know this is physically impossible). I think it should work since all the fluorescent lamps will not turn on at the "same time" (most probably few milliseconds or more than one second different), by the time all fluorescent lamps is turned on, both the relay contact is already closed . Please correct me if I'm wrong.
 
 
 
 
Warning!
Working with high voltages is extremely dangerous. Use this information at your own risk.
 
Block diagramBlock diagram
 
 Mount Relay on a DIN RailMount Relay on a DIN Rail
 
 
 
Wiring diagramWiring diagram
 
 
This article explain how to connect a ULN2803 to the Arduino. As shown in figure below, I'm using Swiss machined socket for the ULN2803 line driver since the ULN2803 can generate heat & require more current on it especially on pin9 (Gnd), but I agree the best thing is a solid soldered connection. Always remember stay away from using standard IC socket.
ULN2803 PCBULN2803 PCB
 
 
8 Relays inside a box8 Relays inside a box
 
 
8 Relays inside a box8 Relays inside a box
 
 
Close upClose up
 
To turn on relay manually, on/off switch must connect between the output of ULN2803 and relay coil. See figure below on how to adding on/off switch and indicator to the circuit. This is very useful when the controller is not able to control the relays while still want to  turn on the lights.
Adding On Off switch and indicatorAdding On Off switch and indicator
 
 
Figure below shows 10 units on/off switch fixed to the cover, I'm using only 8 of them, the other two is reserved for future use. A key switch is use to prevent manually turn on the relay.
 Cover top viewCover top view
 
 
Cover Bottom ViewCover Bottom View
 
 
As shown in figure below is the final product of the Relay Box. An Arduino is use to control the relay.
Final ProductFinal Product
 
Close-upClose-up
 
This project hab been using for more than 20 months without major problem, the only problem I'm facing is the light inside the on/off swith getting too hot that cause the swith mul funtion. I suggest to use LED for the indicator instead of built-in light from on/off switch.
Read 2942 times Last modified on Wednesday, 22 October 2014 13:53

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