5volt 50ma input, need to output 12 up to 5 amp

[Flyback]

Agreed, but if the coil resistance was very low , there would be really high inrush if the coil current wasn't supplied from a constant current source. Though I agree it is wrong to call it inrush as it is just the high current that will also flow once the current has become constant.
Let us Think of all the power being wasted in solenoids who limit current by resistance, (most of them) the world over.

I see I was worog to call it "inrush", but certainly the build up of current is very fast, not slow like many (other) people think, because they imagine that the solenoid coil inductance is there from the point of turn on, which it isn't.

 

[KeepItSimpleStupid]

I don't want to complicate this discussion, but add stuff:
Search for:
"High side driver"
"Low Side Driver"
"Solenoid driver"

The "solenoid driver" can get to be a little tricky. In a lot of cases you want a "big kick" and then you want to lower the power dissipation.

I had one application which was slightly the opposite. I wanted a "slow kick". This was a shutter next to a one mm thick ($1000 USD) piece of glass. Cycle time was about 2.5 minutes on, 30 sec off, 8 hours of the day slightly variable and manual.

 

[Millennium]

My favorite for Q2 is a 2n3904 (mostly because I have about 250 of them).

For Q1, **broken link removed**. Take your pick. I've sorted to the ones that would work for you...

For Q1 i bought these https://www.digikey.com/product-detail/en/SPP15P10PL H/SPP15P10PL H-ND/2783608

and for q2 i'm using 2n3904


Cant seem to get it to work. Is R1 2.2K?

I'm seeing some voltage changes at q2 collector in response to changes at the base. But nothing from the q1. Sure i'm doing something wrong.

 

[MikeMl]

You understand that the PMOS is effectively connected upside down, with its source tied to +12V, and drain tied to the load:

And, if mounted on a grounded heatsink, you have to use an insulating kit to isolate the tab, which is also the middle pin, drain.

If you have the drain and source reversed, then the load will always be on, with the input having no effect.

 

[Millennium]

I was looking at the datasheet and the posted diagram and realized about the upside down so Yes i have source pin 3 to 12v and drain pin 2 to load with the diode listed in the diagram to protect the spp15p10pl.

I just have the transistor plugged into a breadboard with no heatsink nor grounded heatsink. Right now the load is always off with no response to input.

 

[MikeMl]

I was looking at the datasheet and the posted diagram and realized about the upside down so Yes i have source pin 3 to 12v and drain pin 2 to load with the diode listed in the diagram to protect the spp15p10pl.

...

Did you add an external diode across the PFET? The diode shown on the data sheet is built inside the PFET; no external diode should be wired across the PFET.

Wire a diode across the load being switched if it is inductive, like a motor, relay, or solenoid; diode cathode to PFET drain, and diode anode to Gnd.

In the diagram of post #2, the resistor from gate to source is 2.2K.

Measured with respect to Gnd (0V):
What is the PFET gate voltage when the input is 0V?
What is the PFET gate voltage when the input is +5V?
What is the PFET drain voltage when the input is 0V?
What is the PFET drain voltage when the input is +5V?
What is the load?
What is the load's resistance measured with an Ohmmeter?

 

[Tony Stewart]

Measure each pin voltage ok?

THis would have been a better choice
**broken link removed** Vds=60V Rds(on) = 0.050Ω @Vgs = 5.0 V $1.50

SPP15P10PL H Vds=100V Rds(on) = 0.2 Ω @Vgs=10V $1.55
4x hotter

 

[Millennium]

****, i only chose the one i did because of the "power dissipation". I assumed it could handle more current ie power the 25 ohm solenoid I intinded to drive with a 85 ohm 12 volt relay.

 

[Millennium]

Did you add an external diode across the PFET? The diode shown on the data sheet is built inside the PFET; no external diode should be wired across the PFET.

Wire a diode across the load being switched if it is inductive, like a motor, relay, or solenoid; diode cathode to PFET drain, and diode anode to Gnd.

In the diagram of post #2, the resistor from gate to source is 2.2K.

Measured with respect to Gnd (0V):
What is the PFET gate voltage when the input is 0V?
What is the PFET gate voltage when the input is +5V?
What is the PFET drain voltage when the input is 0V?
What is the PFET drain voltage when the input is +5V?
What is the load?
What is the load's resistance measured with an Ohmmeter?

I'll check those voltages and edit. Load is a 85 ohm automotive relay.

My datasheet did not show an internal diode for the transistor i used listed above.

 

[MikeMl]

...My datasheet did not show an internal diode for the transistor i used listed above.

This makes no sense. I posted a fragment of the SPP15P10PL data sheet in post #24, and it plainly shows the PFET's internal diode, connected cathode to source, anode to drain. What transistor, and what diode are you talking about.

 

[Millennium]

youre right. I was remembering the TIP42 sorry.

 

[MikeMl]

So, did you get it to work?

 

[Millennium]

Yes! Got it working. Problem was both power supplies 5v and 12v were not sharing the same ground on the breadboard.