12v DC soleniod current question 1

[teslaa]

sorry but I am a noob to electronics but here goes.

I have a 12v DC adapter outputting 2amp which and I need to hook it up to a solenoid which is super strong. I tried with a 12v DC 2a solenoid (20N force) and its really really weak. I then tried with a 12v DC 300mA solenoid (6N force) and its super strong however it soon got hot and went bust (over current I assume). Can someone unlock this mystery for me and tell me what the best solenoid I should get for the adapter (I am stuck with the 12v 2a adapter).

12v 2a adapter
Link

12v 2a solenoid (WEAK when working with above adapter, possibly defect?)
Link

12v 300mA solenoid (burned out)
Link

 

[LiteYear]

Although naive, I think in this case you might have actually been unlucky: if the specs are accurate and the quality good, the adaptor should have worked with either solenoid. It's possible the load (a highly inductive solenoid) made the adaptor unstable, but first on why it should have worked:

Probably the easiest way to explain why it should have worked is to point out that the adaptor is a voltage source - it creates a 12V supply and it's the load that determines the current. If it is made to specification, it should continue to supply close to 12V until the load demands more than 2A, after which the adaptor will fail to perform (it may drop the voltage, shut off altogether, blow a fuse or just let the smoke out).

When connected to the 2A solenoid, the supply should have been able to supply the necessary 2A to give you the specified performance. Of course, it's right on the limit of the specified performance, so without going into the detail of a solenoid current waveform, maybe either the solenoid actually demanded a little more than 2A or the adaptor couldn't quite supply 2A, and so the performance was affected. Typically the designer will build in a bit of tolerance to account for these variations, but you get what you pay for.

When connected to the 800mA (I couldn't see 300mA anywhere?) solenoid, the supply should have happily supplied the 800mA. The solenoid should not have burnt out.

So based on the evidence you've provided, and assuming you've wired everything up right (hard to go wrong), I'd suggest that your adaptor is suspect in one of two ways: 1) the inductance of the solenoid was enough to send the regulation of the adaptor unstable and it no longer managed 12V or 2A. 2) the adaptor is actually poorly spec'ed to start with, and was actually outputting more than 12V and less than 2A, under-currenting the 2A solenoid and over-currenting the 800mA solenoid.

In either case, I'd try a better adaptor before worrying about the solenoid. That adaptor looks suspiciously compact for a 24W power supply. Get something a bit beefier.

By the way, make sure you put a flyback diode across the solenoid's terminals - at 2A you could get a nasty voltage spike when de-energising the solenoid.

 

[John2025]

Perhaps the smaller solenoid was not able to pull in completely. That can increase the current and burn out a solenoid in short order. Smarter people than me can explain why.

 

[itsmoked]

John2025; That only affects AC solenoids and the OP is using DC sols.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

I did not see a duty cycle listed in the specs. Many solenoids in vending machines are designed for momentary duty and will burn out if they are energized continuously.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[John2025]

Or smarter people than me can actually read the post. Back to Reading Comprehension 101, I guess.