Author Topic: How to improve Solenoids open/close response time ?  (Read 17118 times)

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Offline AlbatroonTopic starter

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How to improve Solenoids open/close response time ?
« on: March 11, 2019, 07:37:01 pm »
I am designing a board to control Solenoids, I'll use TIP122s to control them.
How I can make them open/close faster ?

I found this circuit online, by adding a zener diode placed in series will improve the the latch-out response.

Source: https://www.theleeco.com/engineering/electrical-engineering/lee-solenoid-valve-drive-circuit-schematics/
Could some one explain how dose this supposed to do so ?
 

Offline rstofer

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Re: How to improve Solenoids open/close response time ?
« Reply #1 on: March 11, 2019, 07:49:58 pm »
When the solenoid is deenergized, the field collapses into the diode and the current flow through the diode and winding keeps the solenoid engaged until the voltage drops to essentially the Vf of the diode and it ceases to conduct.  Adding a zener diode increases the voltage at which the circuit ceases to flow current through the diodes, releasing the solenoid sooner.
 

Offline AlbatroonTopic starter

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Re: How to improve Solenoids open/close response time ?
« Reply #2 on: March 11, 2019, 08:07:07 pm »
When the solenoid is deenergized, the field collapses into the diode and the current flow through the diode and winding keeps the solenoid engaged until the voltage drops to essentially the Vf of the diode and it ceases to conduct.  Adding a zener diode increases the voltage at which the circuit ceases to flow current through the diodes, releasing the solenoid sooner.

Thank you for your replay.
Do you have any ideas how to make it open faster?
 

Offline viperidae

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Re: How to improve Solenoids open/close response time ?
« Reply #3 on: March 11, 2019, 08:20:16 pm »
Increase the voltage if you want it to operate faster
 

Offline soldar

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Re: How to improve Solenoids open/close response time ?
« Reply #4 on: March 11, 2019, 08:43:52 pm »
You can activate it with twice the voltage and switch to lower holding voltage. You can use twice the rated voltage and a resistor and capacitor. Initially it gets twice the voltage but as the capacitor discharges the volatge settles at a lower point. This is good if the solenoid does not consume great power for long periods of time.
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Offline Benta

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Re: How to improve Solenoids open/close response time ?
« Reply #5 on: March 11, 2019, 09:08:44 pm »
It's all about voltage.
If you apply a higher voltage, it will close faster. You'll need to drop the voltage to operating voltage after that, of course.
Same thing when releasing: allowing a higher kick-back voltage will make it faster.
 

Offline unitedatoms

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Re: How to improve Solenoids open/close response time ?
« Reply #6 on: March 11, 2019, 09:09:57 pm »
I remembered nice relay/solenoid bootstrap driver based on precharged capacitor
Finally found the article. It is on last page of this pdf

https://m.eet.com/media/1154107/25323-bootstrap_circuit_speeds_solenoid_actuation_pdf.pdf


Interested in all design related projects no matter how simple, or complicated, slow going or fast, failures or successes
 

Offline CJay

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Re: How to improve Solenoids open/close response time ?
« Reply #7 on: March 11, 2019, 09:12:34 pm »
Research peak and hold fuel injector drivers
 

Offline rstofer

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Re: How to improve Solenoids open/close response time ?
« Reply #8 on: March 11, 2019, 09:17:46 pm »
Thank you for your replay.
Do you have any ideas how to make it open faster?

The fastest it will run is with no diodes but that isn't possible because there is a body diode in the MOSFET.

There is a possibility of some kind of capacitive discharge circuit that forcibly opens the solenoid by driving a reverse current through the inductor.  No, I don't now how to do it and I didn't find much on Google.

Here's a circuit that is interesting but it only works on pull-in:

https://www.electronicdesign.com/analog/what-s-all-solenoid-driver-stuff-anyhow

Basically, you have a lot of stored energy in the inductance and all the time it is discharging, there is current flow through the solenoid.

Here's an idea:  Use Bob's circuit above to pull the solenoid in and then reduce the current to some lower value for hold-in. Now when it comes time to drop out, you have less current flow so less stored energy and the release is faster.  Couple that with the Zener approach and maybe you'll have something.
 

Offline Refrigerator

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Re: How to improve Solenoids open/close response time ?
« Reply #9 on: March 11, 2019, 09:20:56 pm »
You can look into how car fuel injectors operate and how accurate timing is achieved.
I have a blog at http://brimmingideas.blogspot.com/ . Now less empty than ever before !
An expert of making MOSFETs explode.
 

Offline soldar

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Re: How to improve Solenoids open/close response time ?
« Reply #10 on: March 11, 2019, 10:06:30 pm »
Some cars use an ingenious system for the solenoid which activates the starter motor. The solenoid engages the starter gear and also connects the starter motor. The solenoid has two windings; one goes directly to gnd while the other one goes to gnd through the starter motor winding. At first both windings are energized but once the solenoid has moved one winding is no longer active and only the other one is enough to provide holding force.

In any case, there is a mechanical limit on how fast things can move. You can improve a bit by using more voltage to activate and reverse voltage to deactivate but if you need really fast response you will need to design the entire electro-mechanical thing from scratch. For instance, a solenoid with a short travel which moves a lever which amplifies the distance.
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Offline viperidae

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Re: How to improve Solenoids open/close response time ?
« Reply #11 on: March 11, 2019, 10:09:54 pm »
Have a look at this datasheet, it's a peak and hold injector driver.
http://www.ti.com/lit/ds/symlink/lm1949.pdf

The injector opens fast, as 4x normal current is applied, it then lowers to a 1x holding current.
The lower holding current means it turns off faster, as there is a smaller magnetic field to collapse.
 

Online Zero999

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Re: How to improve Solenoids open/close response time ?
« Reply #12 on: March 12, 2019, 02:34:16 pm »
Or remove the free wheeling diode and put the zener in reverse parallel with the transistor.

Yes bootstrapping can be used to double the supply voltage. I did a simulation awhile back with LTSpice.
https://www.eevblog.com/forum/beginners/12v-dc-to-110vac-pure-sine-converter/msg2221902/#msg2221902

 

Offline langwadt

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Re: How to improve Solenoids open/close response time ?
« Reply #13 on: March 12, 2019, 03:38:26 pm »
Thank you for your replay.
Do you have any ideas how to make it open faster?

The fastest it will run is with no diodes but that isn't possible because there is a body diode in the MOSFET.


the body diode is in the opposite direction, with no external diode the flyback voltage will be limited by the mosfet avalanche voltage
which the mosfet might be rated for and and do just fine

 

Offline coppercone2

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Re: How to improve Solenoids open/close response time ?
« Reply #14 on: March 12, 2019, 04:03:57 pm »
I would research what happens to lifetime of these components if you start slamming them with transients.

Is there lifetime literature? It seems like a engineering bear
 

Offline tecman

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Re: How to improve Solenoids open/close response time ?
« Reply #15 on: March 12, 2019, 07:03:47 pm »
Bootstrapping and zener are the way to go.  But be aware that with higher switching duty cycles bootstrapping will increase overall solenoid current resulting in higher temps, and will also increase dissipation in the zener.  Be sure to evaluate both.  Higher zener voltage will decrease off times, but the limits are the higher voltages on the rest of the switching components.

Paul
 

Offline AlbatroonTopic starter

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Re: How to improve Solenoids open/close response time ?
« Reply #16 on: March 13, 2019, 11:09:10 am »
Wow, A lot of answers. Thank you all guys !
I'll go with Bob's drawings.. Seems that it 'll fit my needs. Specifically the rapid speed operation.
I'll use this circuit


I am using 24v 6.5w solenoids..
What transistors should I use ? Should the 3 transistors rated to this power or only Q3 should be a big one and the others are a small ones ?
If I added the Zener trick to the circuit. Will it help or not ?

By the way, I am driving about 200 solenoids, many times per second.
I started this project back in 2012, I Built this https://youtu.be/YtlYc2bzUEs?t=10.
Now I am trying to build a new one with batter valves, better performance & a Bigger size !
 
Thank you all !


« Last Edit: March 13, 2019, 11:37:36 am by Albatroon »
 

Offline AlbatroonTopic starter

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Re: How to improve Solenoids open/close response time ?
« Reply #17 on: March 16, 2019, 02:39:51 pm »
Anyone ?
 

Offline soldar

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Re: How to improve Solenoids open/close response time ?
« Reply #18 on: March 16, 2019, 03:45:28 pm »
That schematic does not look right to me. Why did you make changes to the original?
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Offline AlbatroonTopic starter

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Re: How to improve Solenoids open/close response time ?
« Reply #19 on: March 16, 2019, 04:50:17 pm »
That schematic does not look right to me. Why did you make changes to the original?
Nothing Changed, It's the original schematic from the website
 

Offline soldar

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Re: How to improve Solenoids open/close response time ?
« Reply #20 on: March 16, 2019, 06:27:54 pm »
It doesn't look right to me. I was thinking of the one posted in #6 which looks good mutatis mutandis.
« Last Edit: March 16, 2019, 06:40:45 pm by soldar »
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Offline SilverSolder

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Re: How to improve Solenoids open/close response time ?
« Reply #21 on: March 16, 2019, 06:41:00 pm »
Loved the aqua display in the video - look forward to seeing the new one!   :D

You know, the biggest factor in getting the water "up to speed" may be the water itself!   Maybe the response speed could improve if you had some springy tubes close to the valves that would act as a bypass capacitor for the water, to help it respond quickly!  - also avoid long thin tubes that increase the water's "inductance"...

Maybe do like a car fuel injection system, where a relatively large tube (the fuel rail) feeds the injectors as close as possible,  with a pressure regulator close to the valves.  This is all done to improve the transient response of the injection cycles, sounds like you have the same challenges!
« Last Edit: March 16, 2019, 06:48:02 pm by SilverSolder »
 

Offline AlbatroonTopic starter

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Re: How to improve Solenoids open/close response time ?
« Reply #22 on: March 16, 2019, 06:55:24 pm »
It doesn't look right to me. I was thinking of the one posted in #6 which looks good mutatis mutandis.
I think this circuit have an issue with my application.
I open/close the valves rapidity, on the first time It will work great, But If I opened again after a small time the capacitor will not have charged yet, And the open pulse will not be the same, (I THINK SO) !
That's why I am interested in the mentioned on replay #8, On Fig 3, It all about rapid speed operation, And looks very promising on Scope too.

Accurate open/close voltage every time at high speed.

sounds like you have the same challenges!
Yes I do :D
I am trying to fine tune every piece step by step, After making the control PCBs working as best as I can, I'll play with water flow,pressure And lights to make it better ! Thank u
 
« Last Edit: March 16, 2019, 06:57:49 pm by Albatroon »
 

Offline soldar

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Re: How to improve Solenoids open/close response time ?
« Reply #23 on: March 16, 2019, 07:37:03 pm »
I open/close the valves rapidity, on the first time It will work great, But If I opened again after a small time the capacitor will not have charged yet,
Oh, OK, I understand now.

One way to deal with that would be to replace the charging resistor with a transistor so the capacitor would charge faster.

If you have many valves in a complex system you wight want to consider having two rails (+V, 0, -V) so you can first connect between +V and -V and then switch to half voltage.
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Online Zero999

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Re: How to improve Solenoids open/close response time ?
« Reply #24 on: March 16, 2019, 08:08:26 pm »
The bootstrapping idea is a good one. Note that each transistor should have its own base resistor, which has been omitted from the schematic.

To improve the turn off speed, a zener diode can be added in reverse parallel with Q2.

Yes, the main drawback with that circuit is it takes awhile for C1 to charge, via R1which will limit the repetition rate. R1 can be replaced with a current source or better still, another transistor. THe Hfe of Q3 will determine the charging current, so there's a bit of "Hfe suicide" here, but it should be fine.
 


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