Fast Snubber for Solenoid Valve

THE_RB

Joined Feb 11, 2008
5,438
...

Finally I use common 4004 diodes, I tested a lot of zenner diodes and they are pretty much the same (5 ms open/close time), as 4004 are cheaper, I used these.
...
That would probably be because you connected the zener diode across the coil (like you connected the 4004 diode?)? :eek:

To use zener diodes as snubbers you need one zener diode (reversed) in series with the 4004 diode.
So the diodes are in series like this;
--->|----|<---

then the diode pair goes across the coil, with the 4004 in the same orientation as you would normally use.
 
Hey folks!

I have been working in the prototype of the "Water Printer". The electronics works like a charm with 0.1 ms precision. Valves open/close time is 6ms, fast enough for me.

Finally I use common 4004 diodes, I tested a lot of zenner diodes and they are pretty much the same (5 ms open/close time), as 4004 are cheaper, I used these.
In your very first post of this thread, you said:

"Actually I´m using one 1N4004 diode parallel-connected to each solenoid. This protection works fine but it has a big controversial issue: the close time is widely increased (by 2x or 3x) and makes my system not to work correctly."

How is it that the "...increased (by 2x or 3x)..." close time is no longer a problem?
 

Thread Starter

Tomas_2

Joined Oct 8, 2011
15
That would probably be because you connected the zener diode across the coil (like you connected the 4004 diode?)? :eek:

To use zener diodes as snubbers you need one zener diode (reversed) in series with the 4004 diode.
So the diodes are in series like this;
--->|----|<---

then the diode pair goes across the coil, with the 4004 in the same orientation as you would normally use.
You are right! I connected the zenner diode incorrectly. In some days I will try and test the alternative you showed me. Thanks!
 

Thread Starter

Tomas_2

Joined Oct 8, 2011
15
In your very first post of this thread, you said:

"Actually I´m using one 1N4004 diode parallel-connected to each solenoid. This protection works fine but it has a big controversial issue: the close time is widely increased (by 2x or 3x) and makes my system not to work correctly."

How is it that the "...increased (by 2x or 3x)..." close time is no longer a problem?
Good point. By that time I was making the first tests and using some big and heavier valves. The comparison between “4004 diode” vs “none” with the newer valves made little difference so I went with the most conservative (and cheaper) alternative: 4004 diode.
 

Rx7man

Joined Feb 17, 2012
3
OK, for a first post here from me I'll dig a very interesting thread up from the grave... I have a lot of experience dealing with the NEED for solenoid valves acting quickly, not so much on the HOW to make them do it, but here's a couple ideas. My experience is in automotive fuel injection, but moreso in the packaging industry where I built machines that make boxes, and as the flat piece of cardboard travels under a glue nozzle, the glue has to be applied uniformly and repeatably. From what I gather from your project, the absolute timings aren't what is important, but that they are all the same, and repeatable. You can always offset the timing to get what you want.


With the number of then needed, you do get some volume discounts,.. so here's what I consider to be the BEST (not cheapest) way of going about it..
An LM1949 injector driver is designed precisely to control solenoid valves, by driving a Darlington NPN (most often) and with a current sensing circuit, it give full power to the solenoid until it detects actuation, then cuts the power back by about 4x to keep it held, reducing power consumption, but more importantly energy stored in the coils, giving them faster and more predictable turn-off times and reduced back EMF.

I'm working on pulsing a 12V solenoid as well, from a microcontroller, looking for about 10ms of resolution, through a 12V 500ma solenoid.
I've come up with a ZTX1051A (TO92 format = small, cheap) NPN which has a typical gain of about 150, Vsat of under 1V and capable of 4A continuous (2A @ 90C) (Voltage leaves a little to be desired at ~70V) with a diode and zener across it as suggested previously.. this only requires 4 components per channel (~$1.25 total)
 
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