BobL
23rd May 2014, 05:23 PM
Another one of my spaghetti boxes for anyone that is interested. Once again the usual warnings and dangers of working with mains voltage apply. This project also uses mains voltage activated relays purely because I already had these and not many activations are needed
The background to this one is as follows.
I have a small compressor that sits outside the shed in a semi-sounprooof enclosure. As most of you will know when you turn a compressor on, it run until the pressure reaches a certain level and then turns itself off. The problem is I forget it's on and because of other noise I don't hear it for the rest of the day and then late in the evening, often while in bed and things are much quieter I sometimes hear the compressor start itself up again. No one has complained but I reckon the neighbours don't need this at night and worse is when I have gone away for a couple of weeks and it has run all this time.
To help me remember to turn the compressor of I even set up a red light near the door that is wired into the Compressor circuit but I still managed to usually walk right past it and not turn off the compressor.
So the aim of the new circuit was to set up a box that would automatically turn the compressor off after a certain hour every day. There are plenty of 10A timers that will automatically stop and start an appliance but there is nothing I'd trust at the 15A level AND I don't want the timer to automatically turn back on again - I want to have that control. Plus while I was at it I thought I would implement an automated Tank vent - Currently I have an irrigation solenoid connected to it and can trigger the venting from inside but I often forget to do it for weeks until the water starts coming out of the air lines.
This is what the box looks like
http://www.woodworkforums.com/attachment.php?attachmentid=314459&stc=1
The enclosure is home made from some ally channel, white PVC and clear perspex scavenged from a Skip at work
The orange power wires underneath are from a 15A extension cord - LHS is power in and the RHS is Power out.
The black plug on the RHS of the box is a 24V~ supply to the venting solenoid on the compressor tank.
The no volt switch (NVS) will start and stop the compressor manually provided the timer is on
The 24 Hour clockwork timer is scavenged from an old timer that has not seen use for ~15 years.
http://www.woodworkforums.com/attachment.php?attachmentid=314458&stc=1
FWIW here is the inside with the front door open.
http://www.woodworkforums.com/attachment.php?attachmentid=314457&stc=1
And here is a sort of circuit schematic.
http://www.woodworkforums.com/attachment.php?attachmentid=314460&stc=1
This is how it works.
Incoming AC power is supplied to the timer, a 30A Power Relay (PR) and a Venting relay (VR2).
The timer is in series with the NVS so both have to be on before the PR will allow current to reach the output to run the compressor.
The Timer is set to cut the power off every night at say 9pm which breaks the power to the compressor but triggers VR2 to switch off allowing 240V to reach the transformer (T) which will open the tank vent valve. (VR2 is wired to deliberately switch the power to the transformer when it is switched off)
When the timer turns the power back on VR2 also turns on and now cuts the power to the transformer so the tank vent valve will close. but no current reaches the compressor until the NVS is triggered manually. This prevents the compressor operating if I am away etc.
The PR ($3.50), VR2 ($4) and the NVS ($13) were purchased on ebay.
It's not necessary to use a 16A NVS but I got these so cheaply it would have been about the same price to purchase a lower current rated switch.
I had a 24V transformer from an irrigation controller but it was too big for this enclosure so I bought this one from Altronics ($13)
All up it probably cost $60 worth of components.
The background to this one is as follows.
I have a small compressor that sits outside the shed in a semi-sounprooof enclosure. As most of you will know when you turn a compressor on, it run until the pressure reaches a certain level and then turns itself off. The problem is I forget it's on and because of other noise I don't hear it for the rest of the day and then late in the evening, often while in bed and things are much quieter I sometimes hear the compressor start itself up again. No one has complained but I reckon the neighbours don't need this at night and worse is when I have gone away for a couple of weeks and it has run all this time.
To help me remember to turn the compressor of I even set up a red light near the door that is wired into the Compressor circuit but I still managed to usually walk right past it and not turn off the compressor.
So the aim of the new circuit was to set up a box that would automatically turn the compressor off after a certain hour every day. There are plenty of 10A timers that will automatically stop and start an appliance but there is nothing I'd trust at the 15A level AND I don't want the timer to automatically turn back on again - I want to have that control. Plus while I was at it I thought I would implement an automated Tank vent - Currently I have an irrigation solenoid connected to it and can trigger the venting from inside but I often forget to do it for weeks until the water starts coming out of the air lines.
This is what the box looks like
http://www.woodworkforums.com/attachment.php?attachmentid=314459&stc=1
The enclosure is home made from some ally channel, white PVC and clear perspex scavenged from a Skip at work
The orange power wires underneath are from a 15A extension cord - LHS is power in and the RHS is Power out.
The black plug on the RHS of the box is a 24V~ supply to the venting solenoid on the compressor tank.
The no volt switch (NVS) will start and stop the compressor manually provided the timer is on
The 24 Hour clockwork timer is scavenged from an old timer that has not seen use for ~15 years.
http://www.woodworkforums.com/attachment.php?attachmentid=314458&stc=1
FWIW here is the inside with the front door open.
http://www.woodworkforums.com/attachment.php?attachmentid=314457&stc=1
And here is a sort of circuit schematic.
http://www.woodworkforums.com/attachment.php?attachmentid=314460&stc=1
This is how it works.
Incoming AC power is supplied to the timer, a 30A Power Relay (PR) and a Venting relay (VR2).
The timer is in series with the NVS so both have to be on before the PR will allow current to reach the output to run the compressor.
The Timer is set to cut the power off every night at say 9pm which breaks the power to the compressor but triggers VR2 to switch off allowing 240V to reach the transformer (T) which will open the tank vent valve. (VR2 is wired to deliberately switch the power to the transformer when it is switched off)
When the timer turns the power back on VR2 also turns on and now cuts the power to the transformer so the tank vent valve will close. but no current reaches the compressor until the NVS is triggered manually. This prevents the compressor operating if I am away etc.
The PR ($3.50), VR2 ($4) and the NVS ($13) were purchased on ebay.
It's not necessary to use a 16A NVS but I got these so cheaply it would have been about the same price to purchase a lower current rated switch.
I had a 24V transformer from an irrigation controller but it was too big for this enclosure so I bought this one from Altronics ($13)
All up it probably cost $60 worth of components.