Automatic (current sensing) DC control with barrel overfill sensor.

[BrianHood]

Completed a build which that turns on a DC whenever the machine(s) associated with it draws power, and senses when the DC barrel is full and kills power to the blower. The priorities for this project were reliability, low cost, and an easy build. Requires five components beyond common wiring materials and an enclosure for an all-in cost of ~$105 (lot of ebay). Build time was five hours (I'm kinda slow) not including rounding up the materials.

Uses a 2hp rated mercury filled relay for the blower, in which one conductor is wired to a metal cup of mercury and the other a probe that is dropped into the cup, eliminating noise, heat, and arcing. Extremely robust.

Thanks to this group for suggesting the Hawkeye current sensor and to a thread over at sawmill creek with the proximity sensor part numbers.

[BrianHood]

A few more details:
A year ago JohnWho? suggested using a Hawkeye 800 current sensing relay to detect/control a DC. I can confirm that works very well.

A proximity sensor can be added to the control loop to a light or alarm when the DC barrel is full. I used a Banner S18P6D photoelectric sensor in a normally closed configuration- when it sees chips, it opens the control circuit, killing power to the DC. It was simpler than an alarm.

I choose to use a TORK TRP-D multi-voltage relay to provide the 24vdc required for the sensor, to detect the state of the Hawkeye, and to switch the high voltage to the contactor coil. The TRP is only rated for 1hp so a second relay was added.

An overide ON switch was added.

Any number of variations is possible, such as remote manual on/off using the TRP low voltage contacts, perhaps at the blast gates. Or just using the proximity sensor for barrel overfill.

[kayak]

I'm interested in the current sensing part of the system.  Could you draw up a quick and dirty schematic of it?

TIA

[BrianHood]

I've had enough interest to buy another set of parts and will build a couple variations, draw up a schematic, etc. I am loving mine, after a couple years of walking across the shop it's like magic when it turns on by itself.

[Underpayedengineer]

I came across this forum and it inspired me to create my own automatic current sensing control instead of purchasing one.  I would like to thanks BrianHood for the inspiration and pointing me in the right direction. 

My setup is a little different.  I have a 240 V 3HP dust collector that I need to come on when I am using any of my power tools.  I used a Packard C340B 3 pole 40 Amp contactor to control the 240 V going to the dust collector.  I used a FRM01 Sain Smart 12v relay cycle timer module for the contactor control.  I placed the FRM01 relay in mode 10 and timer set to 5 seconds.  This will allow the dust collector to stay on for 5 seconds when I turn my saw off.   I also used the Hawkeye 800 current sensing relay that BrainHood and JohnWho suggested above.  I then added a manual switch and a 1ch 433Mhz wireless RF remote control switch to be able to turn the dust collector on and off at will. 

I have been using this design for the last couple of weeks and it has been working great without any issues.  It is nice not having to turn the dust collector on and off manually. 

All the parts above only ran me approximately $45.  They were all ordered off of ebay.  I also had some parts on hand.  Like the 12V 1 amp power supply, 2 amp circuit breaker and manual switch.  The housing and plugs cost as much as the components.  So in all I think I was around $100 for the whole set up.

I will place some pictures below once I figure out how to attach them.

[Underpayedengineer]

Here is another Picture.

[Underpayedengineer]

And another.

[jgt1942]

Completed a build which that turns on a DC whenever the machine(s) associated with it draws power, and senses when the DC barrel is full and kills power to the blower. The priorities for this project were reliability, low cost, and an easy build. Requires five components beyond common wiring materials and an enclosure for an all-in cost of ~$105 (lot of ebay). Build time was five hours (I'm kinda slow) not including rounding up the materials.

Uses a 2hp rated mercury filled relay for the blower, in which one conductor is wired to a metal cup of mercury and the other a probe that is dropped into the cup, eliminating noise, heat, and arcing. Extremely robust.

Thanks to this group for suggesting the Hawkeye current sensor and to a thread over at sawmill creek with the proximity sensor part numbers.

What are the part number or the link to the part numbers in the sawmill creek forum?

[BrianHood]

Completed a build which that turns on a DC whenever the machine(s) associated with it draws power, and senses when the DC barrel is full and kills power to the blower. The priorities for this project were reliability, low cost, and an easy build. Requires five components beyond common wiring materials and an enclosure for an all-in cost of ~$105 (lot of ebay). Build time was five hours (I'm kinda slow) not including rounding up the materials.

Uses a 2hp rated mercury filled relay for the blower, in which one conductor is wired to a metal cup of mercury and the other a probe that is dropped into the cup, eliminating noise, heat, and arcing. Extremely robust.

Thanks to this group for suggesting the Hawkeye current sensor and to a thread over at sawmill creek with the proximity sensor part numbers.

What are the part number or the link to the part numbers in the sawmill creek forum?

Banner S18P6D photoelectric sensor