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Using Arduino => General Electronics => Topic started by: docdockstader on May 21, 2019, 09:51 pm

Title: 3 wire solenoid wiring help
Post by: docdockstader on May 21, 2019, 09:51 pm
Hey everyone, I acquired a portable propane water heater last year in an attempt to heat a very small pop up pool a few degrees.  It worked wonderfully when it worked at all, which wasn't very often.  I contacted the manufacturer, and they were completely unwilling to help beyond very simple troubleshooting steps.  On my own, I determined the heater is extremely sensitive to very light winds due to a single temperature sensor in a very poor location, and the heater is limited to 20 minute run times and has a very poor timer reset routine (basically have to wait all day for it to reset).  I'd like to create my own controller for this unit and I believe it'll be very easy to do so.  My first step was to determine the proper wiring of the LPG solenoid valve, but I cannot find any information anywhere on it.  I have found a product similiar enough I'm sure it's 100% compatible:

https://www.amazon.com/uxcell-Heater-Terminal-Solenoid-Electromagnet/dp/B01DC19LJ4

However, I'm struggling to find any instructions on how to wire this 3 wire solenoid.  Testing the original controller, it seems as if the black wire is ground, and both the yellow and red wires are supplied with 3vdc to open (pull or retract) the valve.  Voltage is completely removed to close (push or extend by spring force) the valve.  I am doubting that's as simple as it is though, because I don't know of any reason it would require two voltage inputs to do the job. 

If I apply voltage to one wire, and gently push the solenoid arm, it retracts very quickly.  If I apply voltage to the other wire, and gently push the solenoid arm, it retracts, but not as powerfully.  If I apply voltage to both wires, and gently push the arm, it retracts most powerfully. 

So...  does anyone know how this device is supposed to be wired?  And, if it truly does require both wires to have 3vdc, can you help me understand why?
Title: Re: 3 wire solenoid wiring help
Post by: wolframore on May 21, 2019, 10:43 pm
Most likely without reading data sheet. Red is power and yellow is signal. It needs both to activate. Full power going to the unit then a smaller signal to let it know to work. Then a low or 0v to close
Title: Re: 3 wire solenoid wiring help
Post by: docdockstader on May 21, 2019, 11:51 pm
I was wondering that as well, but with black to ground and red to 3v, the solenoid actuates and holds fairly strongly.  It doesn't seem to wait for the yellow to go to 3v.  Similiarly, if black is ground and yellow is 3v, it actuates and holds without red being on 3v.  I dunno what this thing is supposed to do...
Title: Re: 3 wire solenoid wiring help
Post by: wolframore on May 21, 2019, 11:55 pm
Sounds like you may have an issue with it.  Try putting ground to yellow at same time  I don't like the design.  It's possible it's a depletion mode PFET type. Not sure. There's no data sheet on some of these Chinese stuff.
Title: Re: 3 wire solenoid wiring help
Post by: docdockstader on May 22, 2019, 12:32 am
I'm concerned applying ground to yellow might cause a short since the original controller seems to never apply ground to either the yellow or red wires.  Is there a way to do that safely?  Thanks for your continued assistance!
Title: Re: 3 wire solenoid wiring help
Post by: MarshaJ847 on May 22, 2019, 01:08 am
This data sheet mentions two coils, Action and Maintain

you would probably apply voltage to both to activate the solenoid and then just keep 3 volts on the maintenance coil until ready to release... I just glanced at it, but read the sheet to be more sure.

Solenoid data sheet (http://www.ekt2.com/pdf/42_SOLENOID_SM.pdf)
Title: Re: 3 wire solenoid wiring help
Post by: Paul_KD7HB on May 22, 2019, 02:00 am
Your solenoid is made for continuous duty. One wire or both are power to make the armature move, and then only one wire is powered to hold the armature in place. The holding connection will be the one with the greatest resistance.

The whole scheme is to minimize the heating of the solenoid coil over the seeral hours it may be activated.

Paul
Title: Re: 3 wire solenoid wiring help
Post by: jremington on May 22, 2019, 02:07 am
You can use a circuit like the one below to control the solenoid (one for each coil). The diode is required.  You will need a separate 3V supply, as the Arduino cannot provide enough current for the activation coil.
(https://forum.arduino.cc/index.php?action=dlattach;topic=617149.0;attach=309325)

Title: Re: 3 wire solenoid wiring help
Post by: wolframore on May 22, 2019, 02:22 am
JR that's a nice circuit if the device is just a solenoid. I believe the driving circuits are built in to work at 3.3v. So over 1.6 activates. Under 1.6 maintains the position and under 0.5 closes it. Yes it should be fine to put ground on yellow to close it.
Title: Re: 3 wire solenoid wiring help
Post by: JCA79B on May 22, 2019, 02:46 am
One of those wires may be from a proof-of-flame sensor, be careful.
Title: Re: 3 wire solenoid wiring help
Post by: docdockstader on May 22, 2019, 03:16 am
Thank you all!  This particular unit has 3 different heat sensors, one being a proof-of-flame.  The proof-of-flame is poorly positioned and overly sensitive so I'll probably reconfigure that some how. 


I'm reading 5.4 ohms between red and black, and 400 ohms between yellow and black.  I can confirm that applying voltage to either red or yellow holds the armature.  As of right now, applying voltage to either red or yellow or both does not move the armature without a little assistance.  I'm guessing the armature is slightly compressed when it's installed in the valve assembly so that's probably not an issue.

I don't entirely understand the schematic.  I understand dig out, R1, R2, C1, and D1.  The logic level n_mosfet appears to be similiar to a transistor? I'm not sure where the solenoid is, or what the component with the backwards E is...  Maybe the backwards E thing is a representation of one of the coils?

Thank you once again, your help is very much appreciated!!
Title: Re: 3 wire solenoid wiring help
Post by: jremington on May 22, 2019, 03:47 am
Quote
I'm not sure where the solenoid is, or what the component with the backwards E is
"M" on its side, stands for Motor, or solenoid.

A MOSFET is a type of transistor and is preferred for this particular application. Be sure to use a "logic level" MOSFET, similar to this one (https://www.sparkfun.com/products/10213).
Title: Re: 3 wire solenoid wiring help
Post by: docdockstader on May 22, 2019, 03:31 pm
Thanks so much!
Title: Re: 3 wire solenoid wiring help
Post by: docdockstader on May 28, 2019, 06:56 pm
Looking at voltage regulators for the 3vdc, is there anyway to know how much power the solenoid will consume? 800mA regulators are easy to come by, would that be sufficient?
Title: Re: 3 wire solenoid wiring help
Post by: Paul_KD7HB on May 28, 2019, 07:03 pm
Looking at voltage regulators for the 3vdc, is there anyway to know how much power the solenoid will consume? 800mA regulators are easy to come by, would that be sufficient?
Are you familiar with Ohm's law?
Title: Re: 3 wire solenoid wiring help
Post by: jremington on May 28, 2019, 07:28 pm
Important facts from the solenoid data sheet:

Quote
Rated voltage DC: 3V
Action coil resistance: R = 5.7 ± 0.2Ω
Maintain the coil resistance: R = 380 ± 20Ω
Title: Re: 3 wire solenoid wiring help
Post by: docdockstader on May 28, 2019, 11:21 pm
Are you familiar with Ohm's law?
I am familiar with Ohm's law, but that's about it.  I know at 3.3 volts and 800mA, the power usage can be up to  two and a half watts, but as I don't have the data sheet for the solenoid, I don't know how much to expect it to use...  I'm sure I'm missing some inference in the question...
Title: Re: 3 wire solenoid wiring help
Post by: docdockstader on May 28, 2019, 11:26 pm
Important facts from the solenoid data sheet:
Thanks jremington!  If my very unskilled math is right... at 3.3 volts and a combined minimum resistance of 354.5, I'm only sitting at about 10 milliamps to actuate the armature.  To then hold it open, I'm closer to 9 milliamps.  I have no idea if that's right.... am I on the right path? 

OR... maybe I don't combine the resistance, so it'd be 600mA for the action coil, and 9mA for the maintenance coil?  Either way... seems like 800mA will be sufficient for this purpose only?
Title: Re: 3 wire solenoid wiring help
Post by: jremington on May 29, 2019, 12:08 am
3.3/5.7 = 578 mA for the action coil
3.3/380 = 8 mA holding.

The combined resistance, for parallel resistors, is 1/(1/5.7 + 1/380) = 5.6 Ohms. There is no point in combining them.
Title: Re: 3 wire solenoid wiring help
Post by: docdockstader on May 29, 2019, 05:57 pm
The combined resistance, for parallel resistors, is 1/(1/5.7 + 1/380) = 5.6 Ohms. There is no point in combining them.
Ah... right.  Thank you!