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Author Topic: Electrical Help for a Push-pull solenoid  (Read 1629 times)
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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.
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It was just a price matter. The P channel was cheaper.
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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.
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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?
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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.

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.

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.
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I think you'll find that the +/- is used to denote "approximately"  rather than "logic + and logic -"  -  but I might be wrong

When I was a student (more years ago than I care to remember) we used a "wiggly equals" sign to denote approximation ≈
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I think you'll find that the +/- is used to denote "approximately"  rather than "logic + and logic -"  -  but I might be wrong

When I was a student (more years ago than I care to remember) we used a "wiggly equals" sign to denote approximation ≈
Maybe you are confusing with the "error" thing , but here is not 20 士1 , it's just 士20.

In fact If you look here
 http://it.rs-online.com/web/c/semiconduttori/discreti/transistor-mosfet/

You can find lot of transistors with 15v -5v value. So i think is intended the range. But i'm not sure actually.


Quote
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.



This is the code of the mosfet:
NTD25P03LT4G it's not an SMD.

btw

The irfz44n is rated 55V , 49A, 士10 , Rds(on)  passed 2volts ( based on grapghic )
http://www.irf.com/product-info/datasheets/data/irfz44n.pdf


So it should fit my case right?
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This is the code of the mosfet:
NTD25P03LT4G it's not an SMD.

I think you will find that it is in the DPAK SMD package. See http://uk.farnell.com/on-semiconductor/ntd25p03lt4g/mosfet-p-ch-30v-25a-d-pak/dp/2101430?Ntt=NTD25P03LT4G and the datasheet that it links to. The datasheet shows the IPAK package as well, however the ordering information lists only versions in DPAK.
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I used a TIP132 at the end, i found one in my scavage box, it's working good, the pushing system is working perfectly smiley-wink
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