Solenoids control using microcontroller?

Thread Starter

cheesemunger

Joined Jan 25, 2009
53
I am getting this solenoid:

http://www.mandeno.co.nz/users/show_item.php?q=6,20,-1,-1,-1,14,74,456,all&key_word=

,but not from there.

I have been told it has a resistance of 35 Ohms. I can run it off 6, 12 or 24 V but I would prefer to run it off 24V. So the Amps it will draw is:

V=IR
I=V/R

V=24 V
R=35 Ohms

I=~0.686A

So I've got that all worked out. I'm just not exactly sure of the schematics or part numbers for the parts? Could any of you help me out?
 

mik3

Joined Feb 4, 2008
4,843
The BD679 says it is NPN but on their datasheet they show a PNP transistor!
Use the TIP102 for sure. Check if it gets hot as to use a heatsink.
 

Thread Starter

cheesemunger

Joined Jan 25, 2009
53
I've looked around some more and seen that the BD675 is NPN. It must have been a mix up on that datasheet. I think I already have some BD675 so I'll try those.
 

hgmjr

Joined Jan 28, 2005
9,027
I have had luck with improved de-energize response times by introducing a zener-diode in series with the standard diode. The zener permits the fly-back voltage to be clamped at a level that will permits the magnetic field in the coil to collapse faster than it would do with only the voltage of a forward biased diode. I'll try to locate the application note that recommended this approach and post it in this thread.

hgmjr
 

KMoffett

Joined Dec 19, 2007
2,918
Cheesemunger,

Did you purchase the solenoid in the link? If so, it's a 6VDC coil and will burn up with 24VDC.

Standard options:
Operating voltages: 6, 12, 24 Vdc
These are for other solenoids.

Just checking. :confused:

ken
 

Thread Starter

cheesemunger

Joined Jan 25, 2009
53
OH, I am not getting it from there, I'm getting from eBay. Now I look at it , its a 12 V one. So I'll have to run it off 12 Volts. This affects the amps, but does this affect any parts I need to get?
 

Thread Starter

cheesemunger

Joined Jan 25, 2009
53
So, this article tells me that I should use a Zener and diode in series with each other but do I really need to? Can I use two diodes in parallel like suggested earlier? I don't want to have to get more parts than I need to...:p
 

hgmjr

Joined Jan 28, 2005
9,027
The configuration I was suggesting was the zener diode in series with a standard diode. If on and off switching times for the relay are not critical then single diode or the parallel diode approach is a tried and true solution.

hgmjr
 

hgmjr

Joined Jan 28, 2005
9,027
A single diode is probably a good starting point for your application.

Is your application going to result in the constant operation of the relay in which it cycles open and closed once every second?

hgmjr
 

Thread Starter

cheesemunger

Joined Jan 25, 2009
53
Mmmm, lets consider this. Ok, it will do 1 every second for 20 seconds then have about a 10 second break then back to start. It should do this for about 20 mins.
 

hgmjr

Joined Jan 28, 2005
9,027
If you plan on using the relay over many thousands of operations then you may want to consider using a suitably rated solid-state relay.

hgmjr
 
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