12vdc Solenoid -- OK to run at 13.7vdc? - Page 1
Forum section: electronics / beginners

author: jstarr
author_rank: Regular Contributor
timestamp: October 25, 2014, 05:27:04 pm
content: Real newbie question. I have an air valve solenoid specified at 12vdc coil (1A) . Can I operate it from a deep cycle AGM battery at 13.7vdc (rated 200 A-h) if fused at say 1.5A or do I need to have a separate regulated 12v 1A supply between the battery and solenoid coil?john

author: Simon
author_rank: Unknown
timestamp: October 25, 2014, 05:33:45 pm
content: it should be fine, if the battery is at rest it will be at no more than 12.5V anyway. Fuse it for 2A a coil will initially draw a lot of current then it will drop off.

author: oldway
author_rank: Super Contributor
timestamp: October 25, 2014, 05:43:57 pm
content: Have a look on the technical specifications of this air valve solenoid.You will find the max and min operating voltages.

author: Seekonk
author_rank: Super Contributor
timestamp: October 26, 2014, 11:52:58 am
content: Running a solenoid at rated voltage is just a waste of power. Hold in is often less than a quarter of pull in current. The quick and dirty way is to place a resistor in series that will drop the current to a hold in value. Parallel with the resistor, place a capacitor of several thousand uF to provide the initial pull in current. Saves a lot of battery current. My projects are micro based and I use PWM to do the same thing.

author: SeanB
author_rank: Super Contributor
timestamp: October 26, 2014, 04:58:52 pm
content: Typically those coils will operate from 9V to 18V, though they will get very hot ( even more so than what they normally do) at the higher voltage. The RC power reduction trick is very common so long as the coil is operated at a low rate, it can be on or off for long periods, but it is not good to try to pulse the coil at a higher rate than the RC time constant. Typically you use 4700uF per amp of pull in current, or for most 12V coils a 10000uF 25V capacitor across the resistor, probably a 4R7 10W unit.Post DC resistance of the coil and those values could be refined further, and the coil part number as well will help.

author: Simon
author_rank: Unknown
timestamp: October 26, 2014, 05:24:41 pm
content: Quote from: SeanB on October 26, 2014, 04:58:52 pmgee, in far less space you could put a little uC module to do the PWM thing

author: SeanB
author_rank: Super Contributor
timestamp: October 26, 2014, 05:46:06 pm
content: Will it survive having 220VAC supplied to it by mistakeIndustrial logic can have some very unfortunate failures, as you get all sorts of signals in the same cable bundle. plus it can be mounted next to the coil, and does not need a fancy enclosure to protect it from whatever you are doing or from water.

author: Paul Moir
author_rank: Frequent Contributor
timestamp: October 27, 2014, 11:55:11 pm
content: Quote from: SeanB on October 26, 2014, 04:58:52 pmYou know, I've seen a SMC pneumatic valve die from being fed unregulated 24vdc (~33). When I quizzed the local guys about it, they said 21-26v and a burnout was quite likely over that.I guess the Japanese expect some precision...

author: SeanB
author_rank: Super Contributor
timestamp: October 28, 2014, 06:30:05 pm
content: I needed a coil one day, and put a 12VAC coil that was in the oddments collection, onto the valve as a temporary coil to get the line up again. It was actually running on 24VAC, but as it was operating for 1 second every 5 minutes I figured it would do until I could get the right coil along with the right valve body. I never actually bothered to change it until I was replacing the air piping a few years later...........Note, the newer generation of Festo valves are a lot less reliable than the old ones. I use Shako where I can not use Numatics, as those are nice, plus you can buy a rebuild kit for them that is cheap and which works. Some of the Numatics valves have 20-30 million cycles on them, and as I needed one rebuild kit for that size I spent 20 minutes extra and rebuilt the other 3 in that spot as well. Just o rings and plastic buffers, and only the o rings were brittle and the one buffer had disintegrated. Bought 4 kits but there are so many rubber parts in the kits I actually only used 2, with all rubber and plastic parts being changed out of those 2 and even had left over parts. They include a set that covers the most complex version of that style, and mine are the base model.