advice on stopping solenoid overheating/burning out

Thread Starter

slatepipe

Joined Oct 2, 2017
23
hi there

https://forum.allaboutcircuits.com/...lenoids-for-kinetic-sculpture-project.140630/

following on from the above thread, i am now further on in this kinetic sculpture project which uses a motorized hoist to move an accordion in and out and 16 solenoids which press keys on either side of the accordion to generate sound, all controlled via a Crestron touchpanel. I have made code for the Crestron processor which then (at the moment) makes the solenoids play chords or arpeggios, or single notes.

At the moment it is a matter of working out which combination of key presses works best with the piece. Although I have run into a problem which hopefully someone here can help me with :

if i have a button on the touchpanel which makes three solenoids press three keys on the accordion to play a chord, which sounds whilst the accordion moves in and out, after about a minute or two the solenoids get very hot, and the other day while testing them, three of them actually burnt out as they were 'high' for too long.

my power supply is a 12v 15A PSU, like this one : https://www.ebay.co.uk/itm/DC-5V-12...hash=item25d974fd0e:m:mXMYO2lbiTGq8KoJbasPG4Q

the solenoids i am using are these ones : https://www.ebay.co.uk/itm/JF-0530B...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

from speaking with a friend who is helping me with the code, it seems i might need a resistor or something in the circuit to stop the solenoids overheating when they are being held 'high' for too long.

can anyone offer any advice to help me solve this problem? if you need any more information please let me know

thanks
 

MaxHeadRoom

Joined Jul 18, 2013
28,617
About the only way you are going to overheat a DC solenoid is too high a voltage, the armature position does not matter as it does in a AC version.
Either that or the solenoid is intended for non-continuous operation.
What is the resistance of the coils?
Max.
 

Hymie

Joined Mar 30, 2018
1,277
hi there

https://forum.allaboutcircuits.com/...lenoids-for-kinetic-sculpture-project.140630/

following on from the above thread, i am now further on in this kinetic sculpture project which uses a motorized hoist to move an accordion in and out and 16 solenoids which press keys on either side of the accordion to generate sound, all controlled via a Crestron touchpanel. I have made code for the Crestron processor which then (at the moment) makes the solenoids play chords or arpeggios, or single notes.

At the moment it is a matter of working out which combination of key presses works best with the piece. Although I have run into a problem which hopefully someone here can help me with :

if i have a button on the touchpanel which makes three solenoids press three keys on the accordion to play a chord, which sounds whilst the accordion moves in and out, after about a minute or two the solenoids get very hot, and the other day while testing them, three of them actually burnt out as they were 'high' for too long.

my power supply is a 12v 15A PSU, like this one : https://www.ebay.co.uk/itm/DC-5V-12...hash=item25d974fd0e:m:mXMYO2lbiTGq8KoJbasPG4Q

the solenoids i am using are these ones : https://www.ebay.co.uk/itm/JF-0530B-DC-12V-1A-10mm-Stroke-Push-Pull-Type-Open-Frame-Solenoid-THl-RDFJ/253487895444?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

from speaking with a friend who is helping me with the code, it seems i might need a resistor or something in the circuit to stop the solenoids overheating when they are being held 'high' for too long.

can anyone offer any advice to help me solve this problem? if you need any more information please let me know

thanks
Based on my experience of solenoids, they can get quite hot under continuous operation – maybe over 100 degrees C.

If there is poor heat dissipation and/or they are positioned in close proximity to one another, this can exacerbate things.

The operation of solenoids is that they need a certain voltage to ensure that they energise correctly, but will hold at a lower voltage.

e.g applying 12V for 1 second will cause the solenoid to energise, then reduce the voltage to 9V and the solenoid will remain energised, but at a much reduced power draw.

You will need to experiment with the solenoids to have to determine the minimum holding voltage and then build a circuit to achieve the required supply voltages to the solenoids.
 

crutschow

Joined Mar 14, 2008
34,282
Below is the LTspice simulation of a solenoid driver circuit that applies full voltage for a fraction of a second to pull it in, and then the voltage is reduced by R1 to lower the solenoid power dissipation.
The value of R1 is arbitrary and can be increased (or possibly reduced) until the solenoid just stays energized.

Note that the power dissipated in R1 is significant, equal to [12V/(R1+12Ω)]² * R1 so the appropriate resistor wattage rating must be selected along with its resistance value.

What is the circuit that drives the solenoid now?

upload_2018-4-15_9-20-16.png
 

MaxHeadRoom

Joined Jul 18, 2013
28,617
I am surprised they burnt out at only 12w, there are many similar solenoids operating in continuous mode with higher wattage than this.
Max.
 

Thread Starter

slatepipe

Joined Oct 2, 2017
23
From here: http://www.icstation.com/0530b-dc12v-300ma-5n10mm-pull-push-type-solenoid-electromagnet-p-7404.html
Note please don't power for a long time.Just about seconds.

Either you need a continuously rated solenoid or you might be able to use a circuit which applies 12V briefly to pull in the solenoid and then reduces the voltages to just enough to hold it in.

hi - thanks for all the replies.
it seems that the solenoids i am using aren't really suited to being powered on for any length of time, which is due to my inexperience. so it looks like my options are :

1. use continuously rated solenoids - in which case would anyone know of a type that are similar in size and perform a similar action to the ones i am using already? some of the ones i am seeing online seem quite different

2. make a circuit that applies 12v to turn them on and then reduces the voltage a little to hold them in but stops them getting hot. Although my experience of this type of thing is fairly limited, so a little guidance on this direction would be appreciated too. how would i test the holding voltage? would it involve a potentiometer?

thanks again
 

MaxHeadRoom

Joined Jul 18, 2013
28,617
What is the period of time you need them on?
Anything more than a short pulse? If so there is latching solenoids that once operated require a short opposite pulse to release them.
Max.
 

ebp

Joined Feb 8, 2018
2,332
From the photos it looks like the solenoid is quite small, so it doesn't surprise me that it would get very hot at 12 watts. I note there is a 300 mA version of the solenoid available and suspect it is rated for continuous operation.

Without resorting to more elaborate drivers, you may be able to reduce the temperature rise with just a series resistor for each solenoid. The force applied by the solenoid is directly proportional to the current through it, but the power it dissipates is proportional to the square of the current. If you reduce the current a modest amount you may still be able to get sufficient force while reducing power. The temperature rise is approximately proportional to the power in the coil.

The coil resistance must be 12 ohms, since it is rated at 1 ampere at 12 volts. If you put a 3.3 ohm (a standard value) resistor in series with it the current would be reduced to
12 V/(12 + 3.3) ohms = 0.784 A,
so you would get about 78% of the force. The power would drop to
0.784^2 A * 12 ohms = about 7.4 watts,
which is a big reduction. The resistor would dissipate
0.784^2/3.3 or about 2 watts.
There are resistors rated at 2 watts, but they too will run hot at rated power. A resistor rated at 3 to 5 watts would be better.

Without some numbers to quantify the force required on the keys the only way to assess if this will work is to do some experiments. If you have to buy resistors for testing, I recommend getting several values such as 2.2, 3.3, 4.7 and maybe even 5.6 ohms. Find the highest value that will work, then consider using the next lower value to have some confidence margin. Again, remember that the resistors will get quite hot.

You may be able to adjust the voltage of the power supply. Just setting it to the minimum may help without using resistors, but adjustability also gives you some tweakablility if you use resistors but find you'd like a value between the easy-to-get values. Usually power supply adjustment range is no more than about ±10%.

One advantage to using a resistor versus a circuit with a capacitor is that the resistor circuit does not have a "recovery time" requirement, whereas capacitor circuits do. The recovery time for a cap circuit may be totally acceptable, but it may be limiting for 128th rests - or something less silly. The resistor does slightly slow the solenoid pull-in, both due to the reduced force and because it increases the L/R (inductance divided by resistance) time constant.
 

Thread Starter

slatepipe

Joined Oct 2, 2017
23
Did you read my post #6?
hi , yes, sorry. i'm quite a newb at electronics though so i'm trying to understand it.

at the moment the circuit is powered by 12v from the mains transformer, this 12v is then looped into each solenoid from a Crestron solenoid switcher - one of these : http://www.quickscreen.no/userfiles\Crestron_CH-HREL8-D6_manual.pdf
this then lets me turn the solenoids on and off using the Touchpanel. the returns for each solenoid are then all joined together using Wago connectors
 

Thread Starter

slatepipe

Joined Oct 2, 2017
23
What is the period of time you need them on?
Anything more than a short pulse? If so there is latching solenoids that once operated require a short opposite pulse to release them.
Max.
hi - ideally i'd like them to be on for varying amounts of time, from a short pulse, up to quite a few seconds so that they would play longer droney chords

i can make buttons on the touchpanel that either pulse the solenoids when pressed, and release them when i take my finger off. or they can latch as well, so one push is on and a second push is off
 

Thread Starter

slatepipe

Joined Oct 2, 2017
23
hi again - regarding the CH-HREL8-D6's - my Crestron friend just came back to me - he said "when they normally talk about inductive loads they mean quite large electric motors that act as an inductor as they have loads of coils in them. The massive inductance causes the relay contacts to arc when they open which can cause problems. I would think the solenoids are so small it won’t be a problem at all"

so i'm relieved with that :)

and regarding the BEMF diodes - i'm not using them across the solenoids. would they help with the burning out issue?
 

MaxHeadRoom

Joined Jul 18, 2013
28,617
The diodes are a wise choice, especially if the contacts are not 'Inductive' rated.
Did you ask what the maximum the relay contacts in the unit are actually rated for? If possible the part number of any relay used.
In4007 (1n4001 and up) for diodes, reverse biased connected. per post #6.
Max.
 

crutschow

Joined Mar 14, 2008
34,282
Here's my circuit modified to operate from a relay output as I understand you have.

It uses an added N-MOSFET transistor to momentarily connect the full voltage across the solenoid until it pulls in.
The value of R2C1 determines how long the full voltage is applied.
The values shown give a pulse of some over 100ms, which should be sufficient.

Then the current drops as determined by resistor R1. For the shown value of 20Ω, it will be dissipating near 3W so should be a 5W resistor.
I also added a diode across the solenoid to protect the relay contacts and MOSFET from its inductive spike when turned off.

upload_2018-4-15_12-43-44.png
 
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