What would an ideal Q2 be? Something like an FQP7P06 ? This particular datasheet does not indicate that the tab is connected to any of the pins (I know that's a thing to be careful of on BJT's).
Since I'll be moving 2.5 amps (30 watts) through it, I assume a heatsink of some sort would be a good idea? If the tab is in fact electrically isolated, I could just run an aluminum bar across the tabs.
magnethead494:
What would an ideal Q2 be? Something like an FQP7P06 ?
It'll do the job. You could look for one with a lower on resistance and Id. It would be uncommon for the source or drain to not be connected to the tab.
Since I'll be moving 2.5 amps (30 watts) through it, I assume a heatsink of some sort would be a good idea? If the tab is in fact electrically isolated, I could just run an aluminum bar across the tabs.
You're using the MOSFET as a switch. A typical FQP7P06 would have an Rds(on) of about 350m ohms at 2.5A. Power dissipation at 2.5A would be (2.5A)(2.5A)(350m ohms) = 2.2W. A heatsink is still needed.
dl324:
It'll do the job. You could look for one with a lower on resistance and Id. It would be uncommon for the source or drain to not be connected to the tab.You're using the MOSFET as a switch. A typical FQP7P06 would have an Rds(on) of about 350m ohms at 2.5A. Power dissipation at 2.5A would be (2.5A)(2.5A)(350m ohms) = 2.2W. A heatsink is still needed.
Thanks. So i'll need to heatsink them individually somehow without allowing them to touch eachother, I take it. (I still find it odd the datasheet doesn't specify). Or use nylon nut and bolt and thermal pads.
magnethead494:
I still find it odd the datasheet doesn't specify
You are right! The datasheet is missing that critical detail. The tab is almost always the same as the middle pin on any TO-220 package; they are presumably punched in one piece.
Mind you, that datasheet is actually from 2001 (down near the bottom). That really is a rather poor device for your application, you would be much better off using a modern part requiring no heatsink. If it is a SMD part, just use these adapters:
The chip plus the adapter will be no bigger than the TO-220 itself. You will have a vastly more compact assembly.
Paul__B:
You are right! The datasheet is missing that critical detail. The tab is almost always the same as the middle pin on any TO-220 package; they are presumably punched in one piece.
Mind you, that datasheet is actually from 2001 (down near the bottom). That really is a rather poor device for your application, you would be much better off using a modern part requiring no heatsink. If it is a SMD part, just use these adapters:
The chip plus the adapter will be no bigger than the TO-220 itself. You will have a vastly more compact assembly.
What would be a better P-channel Mosfet? I've only done a few pieces in SMD and none of them were exactly pretty; granted 3 pins on an 0.1 spacing is easier than 10 pins on a .0254 spacing.
Well, this one would be an excellent choice but is in a "DPAK" format - small but somewhat easier than a SOT-23.
This old one would appear to be adequate, not logic level but since you are going to drive it with at least 10 V, it should switch your 2.5 Amps easily with no heatsink.
And it is in a TO-220 package.
(By all means, someone can check my reading of the datasheets. )
Well, this one would be an excellent choice but is in a "DPAK" format - small but somewhat easier than a SOT-23.
This old one would appear to be adequate, not logic level but since you are going to drive it with at least 10 V, it should switch your 2.5 Amps easily with no heatsink.
And it is in a TO-220 package.
(By all means, someone can check my reading of the datasheets. )
I work 1 block from Mouser Headquarters, so I've been going through their website. I just don't know how to tell crap from, well, not crap...on top of limiting options by minimum voltage and current load.
Question: So using a ULN2803A as the low side driver to drive the FQP27P06 P-Channel QFET high side driver, what resistor do I need as a pull-up on the gate of the QFET? Just a 10K, or is there a specific value?
The mosfets are logic level so you can drive them directly with an arduino output.
You might want to add 1k series resistor on each gate and 10k resistor from gate to GND.
Paul__B:
You are right! The datasheet is missing that critical detail. The tab is almost always the same as the middle pin on any TO-220 package; they are presumably punched in one piece.
Mind you, that datasheet is actually from 2001 (down near the bottom). That really is a rather poor device for your application, you would be much better off using a modern part requiring no heatsink. If it is a SMD part, just use these adapters:
The chip plus the adapter will be no bigger than the TO-220 itself. You will have a vastly more compact assembly.
This is to build a display for automotive lighting, as a demo sequencer for Switchback bulbs, trailer electronics, and third/fourth brake light assemblies.
Re:links I am used to the auto-parse of Xenforo and vBulletin
I have photoshop on my home computer and could have drawn that there, but not on my phone here at the workplace.
But yes, that's an accurate drawing for this project.
Should I include a 100 ohm current limiting resistor between the darlington collector and the MOSFET gate? For 3 cents each i figure it can't hurt.
Also, on the 7 volt LDO (to feed the VIN of the pro-mini), I seem to recall that there is supposed to be a supporting circuit for them to prevent oscilation. I'm not seeing one in the datasheet, so I assume everything is integrated?