Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Increase Solenoid Activation Time

Status
Not open for further replies.

sheltonfilms

New Member
I have a pneumatic solenoid valve shown **broken link removed**.

The black box on the end is the coil and when it energizes it pulls a rod in the middle of the assembly. Once its starts pulling air pressure opens it up faster.

The highest cycling time I can get is 60ms (you can see this here). I need it to be really fast, like less than 1ms cycling time.

Is there a way using external circuitry to decrease the energize time?

I just going out on a limb here and thinking that adding some resistance in series with the coil will lower the time constant, and therefore decrease the energize time. Oh course I could be wrong.

Thanks for your input and time!

The reason for the faster times is for possible position control of the pneumatic actuators. I read somewhere (I think an IEEE report) that you can control position using PWM to the valves. What ever the duty cycle is, that will be the position of the pneumatic rod. The frequency determines the position ripple, but the frequency is limited to the frequency that the solenoid valve can handle.
 
Do we know what frequency the valve can handle?
Do you have a Schematic Diagram of the Circuit board used in the Video?
Maybe you can change a Capacitor on the circuit board or add a Potentiometer to the RC Circuit on the board.
 
A solenoid needs current. The more the merrier. Adding series resistance hinders current. Inductance hinders you too, try 2 solenoids in parallel, half the inductance means half the time. What happens on the return stroke, is the spring fast enough?
I don't know how much air you need but a fuel injector from an automobile is a fancy solenoid that can work fine at 1ms.
 
Hi,

5/2 solenoid pneumatic valves normally require auxiliary air pressure for proper function.

3/2 valves are operated without auxiliary pressure and hence can be cycled at higher speeds.

(3/2 valves can be compared with an SPDT switch with one pressure port, an exhaust port and a bleed port).

If you need fast movement of your actuator you might connect a suction pump to the bleed port enabling the actuator to move in either direction quickly. Suction pumps are available at PIAB (UK). They have no moving part or a motor and generate negative pressure by the use of positive pressure through a nozzle system.

PIAB pumps are very small (about 1/2 the size of a cigarette package) and need filter (cleaning or replacement) at regular intervals if the compressed air contains oil.

At 4bar input pressure the generated negative pressure is -2bar consuming 16l of compressed air per minute. You might reduce the air consumption by controlling the suction pump on demand using another solenoid valve.

Boncuk

P.S. Here is an image of the PIAB mini. Note the M5 input port for pressure and the G 1/8 for suction.
 

Attachments

  • PIAB-MINI.jpg
    PIAB-MINI.jpg
    15.3 KB · Views: 225
Last edited:
Is there a protection diode across the solenoid coil? If so, that greatly slows the release time of a solenoid. You can add an inverse zener diode in inverse series with the protection diode to speed up the release.
 
I know that any signal with a period less than 60ms is applied, the coil just hums.

I have a 5V pulse wave going to the Base of a TIP3055 (1k resister in series), both the board and the car battery are grounded to the Emitter, the positive side of the battery goes to the coil and the other side of the coil goes to the Collector. And I do have a 1N4004 diode on the coil to protect the transistor.

On a 3/2 valve is it just a input pressure, output, and exhaust? I would have thought that the air pressure assisted valves would be faster.

BTW the valves open and close at the same speed. If there is a difference it is very very small.
 
In the first link you gave it has a specification chart that gives the speeds the valve will operate at;
"Highest Action Frequency 5 Cycles/Second"
"Shortest Excitation Time 0.05 Second"

You probably can't change that, it's part of the physical limitation of the valve its self. Like Jaguarjoe said a fuel injection valve is probably your best bet. You may have to make your own manifold to connect/adapt it to you needs.
 
Your going to have trouble getting a valve to run at 1 KHz. Might want to search for a high speed valve.

You could speed up the pull in by running it from a 24 volt supply with a resistor in series and a large capacitor across the resistor. This would reduce the electrical time constant, but from the video it sounds like the mechanics won't run at 1 KHz. (Stroke to long, high mass etc.)
 
You say "Decrease the energize time" and then say "Increase the cycle time". Aren't these mutually exclusive?

I reduced the energize time of a DC solenoid using a PWM kit. I just basically used the slow start aspect of the kit. It worked really well because I had a very thin $1000 spectral shaping glass filter nearby.
 
The only way to decrease the pull-in time of a solenoid is to drive the coil with a short-duration voltage pulse that is several times higher than the rated DC voltage for the coil.

If the solenoid relies on a spring to return it when the coil is de-energized, then not using a snubber diode, and letting the voltage spike to hundreds/thousands of volts will help. Making the spring stronger will help. If the plunger is a magnet, then driving the coil with a short duration high voltage pulse of the opposite polarity will help, too.
 
I have a 5V pulse wave going to the Base of a TIP3055 (1k resister in series), both the board and the car battery are grounded to the Emitter, the positive side of the battery goes to the coil and the other side of the coil goes to the Collector. And I do have a 1N4004 diode on the coil to protect the transistor.
As I stated, you can reduce the turn-off time of the coil by adding a zener in inverse series with the 1N4004 diode. The maximum zener voltage should be somewhat less than the absolute maximum TIP3055 collector-emitter voltage of 70V minus the supply voltage. For a maximum 15V battery voltage it should be less than 70V -15V = 55V. To allow margin, the zener voltage should probably be no more than 45V.

The addition of this zener should noticeably speed up the turn-off time of the solenoid.
 
Look at IGBT ignition coil driver transistors, they have built in back emf protection that does not slow the collapse of the field because of their ~400v protection zeners across C & E. 1N4001's across the coil will slow it down by a considerable amount. You need buckets of current through that coil to initially open it quickly then less current to keep it open, then the coil needs to be unfettered to close i quickly.

If you want to experiment with a PIAB vacuum generator, send me your name/address off list. You can have it for the price of the postage. I got it to make a small inexpensive vacuum "pump" to evacuate auto A/C systems but it didn't quite get there.
 
I would have thought that the air pressure assisted valves would be faster.

It's called a pilot operated valve. The air does not "assist" the solenoid. The solenoid runs a pilot valve which operates the main valve. Pilot operated valves can get by with smaller, lower power solenoids. If you've got a port to connect a separate air supply to the pilot valve, you can run it at higher pressure and the main valve at a much lower pressure. Doing so might double the speed but it won't get you anywhere close to 1 KHz. It doesn't look like that valve has a separate pilot port though. Most of the small ones don't.

I'm pretty sure that chart is wrong because I'm able to get almost 17 cycles a second.

Switching to a specialized, direct solenoid operated valve could get you above 100 Hz which likewise isn't anywhere near 1 KHz. Most of them aren't that fast, the ones we use here would probably only get to 60 Hz before they started skipping.

Highest action frequency is given for the minimum pressure required to run the pilot valve for the valve's rated life. Those valves will run much slower at about 30 psi and probably quit working altogether at about 15 psi. The filtering and lubrication system here is less than ideal so our pilot operated valves usually slow down as they age. I believe the pilot valves simply get dirty and sticky and start to leak a bit over time.

The direct solenoid operated valves are less affected. They might even get faster as the seals wear. I'm not sure. We only use them in a few places because they're more reliable at 3-5 Hz and never run them any faster.
 
I'm curious what your application is. It would help to know what you want to control.

Solenoid valves can be moved to positions between fully open and closed by applying a higher frequency PWM signal. This is very common in automotive use (like EGR valves/solenoids). This is also used in nitrous oxide systems for cars to vary the amount of nitrous injected by modulating the solenoid valve.

However, this only works with a "normal" spring loaded solenoid valve.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top