Calling solid state geeks

[EL34]

I am not at all versed in solid state circuits and so I need some help with a special project


I use CR Magnetics current sensors to sense when a machine in my shop is running
I have been using one of these sensors for many years that turns on a dust vacuum system as soon as a machine is running
I have one current senor inside a big power strip
All the machines plug into that power strip
So any machine plugged into that power strip can turn on the dust vacuum motor

I have been feeding that DC into a device that can turn the AC power on and off to my dust vacuum motor
That all works fine

So now I want to add individual current sensors to each machine
When a machine is turned on it can open the blast gate for that machine only
The other blast gates stay closed
As it is now, I have to manually open and close the blast gates myself

The current sensor outputs an AC voltage based on how much current it senses in the power cord of the machineThen I rectify the AC with a bridge to get DCThen a 4700uf cap smooths the DC out

The DC level ranges from 15vdc to 5vdc, depending on the power of the machine

What I need is a simple circuit that can take the variable DC voltage from the current sensing circuit
Then it connects the relay coil minus to ground to activate the relay

I am guessing one part of the circuit involves a voltage regulator to regulate the variable DC coming from the current sensing circuit?

I am hoping that a few simple components can get the job done here?

Here's some pics of the relay board I have and the current sensing circuit

[shooter]

this is my quick thought, LM339.  I've used it over the years.
basically when the input reaches a pre-set threashold, the output will change, and can be "conditioned" for neg or pos.  your controller board appears "ready" to accept a conditioned signal (hi/lo).

still looking, but out for awhile, soo..

here's the 1st link I grabbed;

http://www.bristolwatch.com/ele/vc.htm

[EL34]

this is my quick thought, LM339.  I've used it over the years.
basically when the input reaches a pre-set threashold, the output will change, and can be "conditioned" for neg or pos.  your controller board appears "ready" to accept a conditioned signal (hi/lo).

still looking, but out for awhile, soo..

here's the 1st link I grabbed;

http://www.bristolwatch.com/ele/vc.htm

The relay board only let's you sink the coil ground to activate the relay coil
The relay + is always connected to +5 vdc


So the circuit has to do that :)
Thanks for your help

[shooter]

another simple circuit that should work

stole from here;
https://www.allaboutcircuits.com/textbook/experiments/chpt-6/voltage-comparator/

[shooter]

even simpler circuit.  need some actual values to "guess" at the base resistors, but basically if your input VDC is ~ > .7vdc that will turn on the transistor, once on it acts a short to make the relay engage.  once your input drops below ~~.7vdc transistor cuts off, relay opens.

[EL34]

Thanks, I'll check it out some more later

[PRR]

OK, after several iterations, shooter hit not only the same idea but nearly the same image I was going to post.

You don't have to "regulate". A BJT will tolerate large overdrive through a resistor. You do want a pull-down resistor to cover base leakage.

[EL34]

Thanks guys
Busy day, I will check back later

[shooter]

one quandary;  If current fluctuates enough the "Load" might cycle, guessing electrically isn't a big deal and  the added latching/smoothing circuitry may not be worth the effort 

[EL34]

I will test PRR's version first
I think I have some of those transistors here somewhere


No dice, I did not have any 2N2222's
I needed something else on Amazon and so I ordered some 2N222's also

[PRR]

> on Amazon

I know about Amazon habit, and you should have some good transistors in the house; but....  if you'd told us about this "relay board" we cudda saved you time.

http://henrysbench.capnfatz.com/henrys-bench/arduino-output-devices/5-volt-4-channel-arduino-relay-module-user-manual/

This is NOT just a relay board, the way we old farts think of one. There's a bunch of front-end. All you really need to do is add say 2k 1/4W resistor in series. The front-end accepts 0-5V signals. Your 15V signal just might burn-out the flea-size 1k on board. But 3X resistance will scale up to your hot signals and keep heat down.

I'm on my Chromebook, away from my image editor, so no piture now.

[PRR]

Dooed onmy Chromebook. Boy what a pain.

[shooter]

can't find the schematic, here's the front page from the pdf of the board I've been using for years. (PDF to big to post).
 Like PRR said, I have to scale or condition the inputs.  used it for solar arrays, autonomous simple rover bases, even built a rain water toilet tank filler 

[EL34]

> on Amazon

I know about Amazon habit, and you should have some good transistors in the house; but....  if you'd told us about this "relay board" we cudda saved you time.

http://henrysbench.capnfatz.com/henrys-bench/arduino-output-devices/5-volt-4-channel-arduino-relay-module-user-manual/

This is NOT just a relay board, the way we old farts think of one. There's a bunch of front-end. All you really need to do is add say 2k 1/4W resistor in series. The front-end accepts 0-5V signals. Your 15V signal just might burn-out the flea-size 1k on board. But 3X resistance will scale up to your hot signals and keep heat down.

I'm on my Chromebook, away from my image editor, so no piture now.

Thanks PRR
Those same relay boards are used by many of the Ardy guys because they are everywhere on Amazon and Ebay
I think I already tested having the current sensor do the work
It does not produce enough current to pull down the relay coil

You can get them for less that $10 on Amazon
You can get them way cheaper if you are willing to wait for them from China

[sluckey]

This looks like a good solution. Cheap too!

https://www.banggood.com/5V-4-Channel-Level-Trigger-Optocoupler-Relay-Module-For-Arduino-p-1343143.html?rmmds=search&cur_warehouse=CN

[EL34]

This looks like a more eloquent solution. Cheap too!

https://www.banggood.com/5V-4-Channel-Level-Trigger-Optocoupler-Relay-Module-For-Arduino-p-1343143.html?rmmds=search&cur_warehouse=CN

Thanks

[sluckey]

Amazon has the same thing but at twice the cost of Bangood. Probably get it faster though.

https://www.amazon.com/dp/B07K5D7XNW/ref=sspa_dk_detail_4?psc=1&pd_rd_i=B07K5D7XNW&pd_rd_w=50ZLL&pf_rd_p=8a8f3917-7900-4ce8-ad90-adf0d53c0985&pd_rd_wg=eFePf&pf_rd_r=7QHY5XM3ZR6B8EMVQXVD&pd_rd_r=e121616a-8782-11e9-928e-67b95b04dff4

[PRR]

> This looks like a good solution.

It 'peers to be the "same" thing as the 2ph63091a in the top post, except re-laid-out with screw terminals. Signal goes to an opto-coupler, then a BJT booster, then the relay. By lifting a jumper the opto input is *totally floating*.

[EL34]

I think the relay Sluckey linked to can be changed from High to low level triggering with those 4 jumpers?

[sluckey]

The 5-15v levels from your current sensor/rectifier modules can probably be dealt with right at the relay module by using a simple diode clamp. This consists of a series resistor and a diode connected between +5V and the input terminal (cathode to +5V). When the input voltage exceeds +5V the diode will become forward biased and 'clamp' the signal at the 5V level.

[EL34]

The 5-15v levels from your current sensor/rectifier modules can probably be dealt with right at the relay module by using a simple diode clamp. This consists of a series resistor and a diode connected between +5V and the input terminal (cathode to +5V). When the input voltage exceeds +5V the diode will become forward biased and 'clamp' the signal at the 5V level.

Thanks for that tip

[EL34]

Got the 1N2222's and built a custom turret board around the 4 channel relay board

There was no need for the diode clamp, the circuit seems to work just fine without it, (so far ) :)
There 4 of the 1N2222 switching circuits on the board
That circuit works great
The current sensors trigger the relay's perfectly when a AC device is plugged in


I am using a 6.3 vac 6 amp power transformer as a test power supply
I set up a full wave bridge and a 5 volt volt regulator to get smooth 5 volts DC.
I added 4700uf/16v cap to that power supply

So all that works great

The other part of this conglomeration is a 12 volt door lock motor that open and closes the blast gate
I am running the motor at 5 volts so it opens and closes slower without a hard slam bounce
There is another 5 volt relay on that blast gate assembly
It has limit switches that sense when the gate is at full open or full closed

Here's the problem I ran into

When the current sensor circuit kicks in, it sends 5 volts DC to the blast gate relay circuit
Then the power supply voltage takes a nose dive because of the motor is using so much current to start up and move
Then the 5 volt blast gate relay coil can't lock down hard
And so the blast gate circuit goes back and forth between trying to open and trying to go back to closed

The 4 relay board does not draw that much powerThe blast gate relay board draws way more because of the DC motor start up current

So I set up a separate power supply to the blast gate motor circuit using a battery and it all works perfectly

I have another power transformer here that has two separate 5 volt winding's
Each winding is rated at 5 volts ac at 3 amps
I wonder if one 5 volt winding would impact the other 5 volt winding?

Here's some pics of my project on the bench
The diagram is the other power transformer I have with the dual 5vac windings

[EL34]

Here's how the blast gate circuit works
The blast gate always returns to closed as soon as power is removed from the relay
This is done using limit switches
Both directions have a limit switch

The blast gate stays open when power is supplied to the relay
Here's a couple diagrams on how it all works
Note that there are four states the blast gate board can be in
The blast gate always returns to closed as soon as power is cut to the circuit from the main relay board that has the 1N2222 current sensor circuits

[EL34]

Instead of one power supply, give the blast gate motor circuit it's own power supply #2
So that the motors do not drawn down power supply # 1's voltages

That's the only idea I think will work?
I don't see how I can use one power supply and not have the motor circuit mess with the voltage levels
Unless I added a massive amount of capacitance to the power supply or/and a choke

But since I already have that dual secondary transformer, that should work just fine for creating two power supplies?
It's new territory for me here on this one using motors

Here's both diagrams

[sluckey]

But since I already have that dual secondary transformer, that should work just fine for creating two power supplies?

I think that will be fine. If not, just use a separate transformer for the motors.

[EL34]

Thanks
I have an adjustable power supply board that Andy at Mojo sent me.
I can dial down the voltage to the motor circuit even lower than 5 volts

The motors are 12 volt car door lock motors, but they work way better at 5 volts or under

I am actually testing the motor circuit using a 3.6 volt LiOn battery and they work really nice at that voltage
If you send the motors too high of a voltage they slam back and forth really fast and bounce off the limit switches


They are designed to pull door lock levers and they work great at 12 volts for that

I can save the big heater transformer for another project

[EL34]

OK, it's all working now
Check out the bench test video here