Electrical Help for a Push-pull solenoid

Hi, i have a system with this kind of hitter :

http://www.adafruit.com/products/413

This hits a lever that should release a spring.

But it has not enough streanght to release the spring even adding some voltage.

So i build another system.

With few coil the system shoot really hard but generate a lot of heat. With more coil the system burned my npn transistor. Is there any kind of diod or "safe" to put in this system? Or i need a biggher transistor?

It's rated 60v , 8amp

It's rated 60v , 8amp

That will take a transistor rated for such a load, but you didn't state what transistor number you used. A logic level N-channel mosfet would be a good choice. Also you should wire a diode across the solenoid's terminals, cathode wired to the +12v side of the solenoid.

Lefty

the npn transistor is the bdx53C. Thks for the advice.

Blu-Vector: the npn transistor is the bdx53C

That would be a very marginal transistor to use as it's max rated current is 8 amps and that would only be met with proper heat sinking. Find a transistor with higher ratings.

Lefty

Blu-Vector: the npn transistor is the bdx53C

Darlington transistors like that one are #4 in my list of things not to use. See http://miscsolutions.wordpress.com/2011/10/16/five-things-i-never-use-in-arduino-projects/ for why. Use a logic level N-channel power mosfet instead, it will run much cooler. And connect a flyback diode in parallel with the solenoid as Lefty says.

dc42:

Blu-Vector: the npn transistor is the bdx53C

Darlington transistors like that one are #4 in my list of things not to use. See http://miscsolutions.wordpress.com/2011/10/16/five-things-i-never-use-in-arduino-projects/ for why. Use a logic level N-channel power mosfet instead, it will run much cooler. And connect a flyback diode in parallel with the solenoid as Lefty says.

Very interessing, i will try to use a IRF540N

Blu-Vector:

dc42:

Blu-Vector: the npn transistor is the bdx53C

Darlington transistors like that one are #4 in my list of things not to use. See http://miscsolutions.wordpress.com/2011/10/16/five-things-i-never-use-in-arduino-projects/ for why. Use a logic level N-channel power mosfet instead, it will run much cooler. And connect a flyback diode in parallel with the solenoid as Lefty says.

Very interessing, i will try to use a IRF540N

Not a good choice as it's not a 'logic level' mosfet and thus can't work to it's full rated values with a 5vdc gate voltage applied which is all an arduino output pin can apply.

Lefty

Waht about this, is rated 30v , 25amp , logic level P channel.

Hi, how often does the hitter have to operate and how long are you pulsing it to make it operate. Tom... :)

Trigger systems like you've made which use high current solenoids invariably do not use what I'll describe as "constant" supply current. Generally the power to drive the solenoid comes from a charged capacitor which is switched into the circuit via the transistor (or better still a FET). This is termed "capacitor discharge" powering. This provides short duration high current, after which the current tails off the virtually zero. The system is frequently used by model train enthusiasts to trigger point switching. However their mode of triggering won't directly suit your application. you will need to include the triggering FET between the system output and your coil (in effect the point control switch referred to in the explanation text.

See : http://www.talkingelectronics.com/projects/CDU-2/CDU-2.html

Note that this text refers to using AC but the system works with DC as well.

I know the method of capacitor discharge but i have a really small compartment to insert electronics, otherwise i really dont need all that pushing power. Thanks for the link.

Hi, how often does the hitter have to operate and how long are you pulsing it to make it operate.
Tom… smiley

It gives a really hard punch so i think just one hit it’s far sufficient, btw to be sure i can operate the solenoid just twice or three time with a delay of 2 sec or more, just to be sure, also operating the solenoid with a too fast trigghering or a “long push” will cause the solenoid to heat up , and we dont want this to happen :slight_smile:

What about this mosfet it would be fine?

Waht about this, is rated 30v , 25amp , logic level P channel. ( sorry the link was missing in the last post )

http://www.onsemi.com/pub_link/Collateral/NTD25P03L-D.PDF

It was recommended that you try:

Use a logic level N-channel power mosfet instead

What made you decide on P channel? Your solution will become more complicated with that device.

A p-channel aint so bad... inside your function

Void setstate(boolean state) ..... state != state; digitalWrite(pin,state);

Wiring is a little different though.

cjdelphi:
A p-channel aint so bad… inside your function

Void setstate(boolean state)

state != state;
digitalWrite(pin,state);

Wiring is a little different though.

The OP is running the solenoid from +12V, therefore if he uses a P-channel mosfet then he will need to level-shift the gate signal. Using an N-channel logic level mosfet is simpler.

dc42:

cjdelphi:
A p-channel aint so bad… inside your function

Void setstate(boolean state)

state != state;
digitalWrite(pin,state);

Wiring is a little different though.

The OP is running the solenoid from +12V, therefore if he uses a P-channel mosfet then he will need to level-shift the gate signal. Using an N-channel logic level mosfet is simpler.

I was under the impression to switch on the P-channel, sinking it to gnd/LOW would switch it on? Or the problem being switching it off!

Use an NPN transistor to switch the P-FET then?

cjdelphi: I was under the impression to switch on the P-channel, sinking it to gnd/LOW would switch it on? Or the problem being switching it off!

Use an NPN transistor to switch the P-FET then?

If the source of the p-channel mosfet is at +12V because it is switching 12V to a solenoid, then the gate also needs to be around +12V to keep the mosfet off. So yes, the problem is switching it off. An NPN transistor can indeed be used to drive the gate from the 5V Arduino output signal. But unless there is a reason to use high side switching, it is simpler to use a logic level n-channel mosfet.

It was just a price matter. The P channel was cheaper.

Blu-Vector: It was just a price matter. The P channel was cheaper.

Then you are not looking at mosfets with similar specifications. N-channel mosfets are generally cheaper than similar P-channel mosfets.

dc42:

Blu-Vector:
It was just a price matter. The P channel was cheaper.

Then you are not looking at mosfets with similar specifications. N-channel mosfets are generally cheaper than similar P-channel mosfets.

So maybe i’m looking wrong, i pay 16€ shipped for a pack of 100 p-mosfets like those with -5v Vgs , 25amp, 30volt. I pay almost the double for thre N kind with same specifics.

I’m looking for Vgs 5v , not more not less. Almost 15amp , and obv at least 12v am i looking wrong? Could someone tell me the near-right specs? The resistence of the coil is 7ohm

Noob question alert:
If a Vgs mosfet is rated Vgs = (+/-) 10 , it means it will be activated by the range -10 , 0 / 0, +10 , or it need the min and max value of -10 / +10?

Blu-Vector: So maybe i'm looking wrong, i pay 16€ shipped for a pack of 100 p-mosfets like those with -5v Vgs , 25amp, 30volt. I pay almost the double for thre N kind with same specifics.

Can you link to the packs of mosfets? Or at least provide the part numbers? It may be that the P-channel ones are in SMD packages and the N-channel ones are in TO220, which tends to cost more.

Blu-Vector: I'm looking for Vgs 5v , not more not less. Almost 15amp , and obv at least 12v am i looking wrong? Could someone tell me the near-right specs? The resistence of the coil is 7ohm

If the resistance of the coil is 7 ohms and you are running them from 12V, then the steady state current will be less than 2A. The current may be higher while the solenoid is pulling in.

Blu-Vector: Noob question alert: If a Vgs mosfet is rated Vgs = (+/-) 10 , it means it will be activated by the range -10 , 0 / 0, +10 , or it need the min and max value of -10 / +10?

If the rating is +/-10V then you must never apply more than +10V or less than -10V to the gate. To see what voltage you need to turn the mosfet fully on reliably, look at the voltage(s) at which Rds(on) is specified.