I’m salvaging parts from an old Xbox 360 motherboard, and it has 15 of each of these MOSFET’s.
Here i’ve included some info on them, i don’t know how to use them or if they are the right kind.
I’d like to make more transistor relays if possible like in this Thread
Since no one replied, i’m guessing either no one knows or they are the wrong kind. Oh well, no big deal.
The manuals are written under the assumption the user already knows how to use them.
Actually i was looking for a schematic of how to build one, like in the transistor relay thread.
One that works with Hi/Low 5v voltages like the relay switch i made.
No.
They don’t state the values of the resistors. R1, R2, only tells me they are resistors.
If you notice in this attached image, of the transistor relay, i marked exactly what each resistor is, from the list of components given.
I was a cheerleader, classes for electronics like this weren’t available at my school.
I’m fairly good at following detailed instructions, but only if they are complete.
Even with the “attached image schematics” it still took me a little bit to figure out, i got the poles on the transistor reversed.
So a complex schematic, that doesn’t list values, isn’t going to do me any good.
I’m actually quite proud of myself that i can do what i’m already capable of. How many of you know girls that even know what resistors do?
These are electronics forums, similar to this one. Both have hobbyist or project sections, where you can get simple electronics questions answered or simple circuits posted. They helped me !
I wasn’t sure whether to post this here or in the “cheerleader” thread, but decided it belonged here
This site includes an example MOSFET switch example with values and additional information. I hope you find it helpful. brunningsoftware.co.uk/FET.htm The circuit from the site is: http://brunningsoftware.co.uk/Pictures/U-fig10.jpg
It is specifically for a 5VDC supply and specific MOSFETs designed for logic level inputs. It is shown driving an LED (D1 and R2), but these two components could be replaced by another load.
If I had some time and wasn’t too concerned about possibly blowing one of them up, I would try some values and see what happens. Rg appears to just pull the gate down, keep the FET off. I would try EDIT 1m. The Rd is basically the load. It could be a small motor, or a light bulb, or anything that runs off the Vdd (power supply or battery) that doesn’t draw too much current.
Just some general comments I’ve seen about MOSFETs. MOSFETs like to be full on or full off. If they are partly on, they can quickly overheat due to internal resistance. There are “regular” MOSFETs and “logic level” ones. The logic level ones are made for operation with +5v on the gate. The regular ones are usually rated with ~+10v on the gate. Generally the higher the rated voltage, the higher the “on” internal resistance. The N MOSFETs have their drain connected to the + voltage and source to ground. P MOSFETs have the opposite alignment. They are “on” when the gate is connected to grouund and “off” when the gate is connected to to the + voltage. Learn to look at the MOSFET data sheet to see its various ratings.
Ya, these are really confusing for me.
Most of what you guys explained was greek to me.
I only need it to drive a 3.3v <150mA (i think it’s actually only 3v 60mA)
An old radioshack laser module i picked up 5-6 years ago.
It just has 2 wires, ground and voltage, works fine when connected to a 3.3v regulator.
I just want to be able to switch it on and off remotely.
A relay would cost more than i paid for the module, and i have other plans for my relay switch.
So i figured one of my mosfets. Remember guys, i have 25 of these mosfets i can salvage. If one fries, no big deal.
I just don’t know how to use those specific mosfets so i was hoping you guys could figure it out. I wanted to trip it using the 5v from one of the BAP/BB2’s output pins, just set it to high/low for on/off, like i did with the relay.
I was hoping for a 3 wire input setup, GND, 3.3/5v regulated, signal wire. Then have 2 outer wires that would switch open or close.
If it wont work with those mosfets, no biggy, i didn’t invest any money into it or anything.
The Surveyor SRV-1 robot has a pair of lasers powered from a 3.3v regulator, with a 20 ohm resistor in series, and an NPN transistor driven by a 2.7K resistor.
If so, just let me know what R1 resistor to use. And which npn transistor would work best.
2N2222
2N4401
2N3904
Those are the only kind i have, though i might be able to salvage a different kind if you give me the model number.
I wasn’t sure if i needed the diode in the schem, or if the diode should be removed and the remove the wire between the 2 points (obviously).
Also the +V will be 3.3v but the IN> will be 5v cause i want to use P12/P13 on the BB2. To many servos, running out of pins.
KM6VV
I couldn’t find the schem, or that part on the schematics.
My understanding of this stuff is still pretty simple, I can build it, but i don’t know how this stuff works. I just follow the instructions.
that could be simplified a bit when you build it. the diode D1 was used across the relay originally to ensure that the back emf of the relay did not damage the transistor… google back emf to read about voltage spikes, collapsing fields etc. In this case we don’t have a coil of wire, a relay, or a motor, so it isn’t as important. In fact the laser is itself a diode. The circuit now, when power is applied to the transistor opens a switch. power flows towards that diode, and cannot go through (as it is backwards), so it will go through the laser around the diode, into the now open transistor and to ground. You could instead remove the diode, save yourself a part and not worry about it. One other thing, I’m not sure how sensitive your laser diode is to voltage (mine usually accept 3 to 4.5v with no problem) but the transistor, a standard 2n4401 (which will work fine here) will drop about 0.3v. So a 3.3v battery will leave 3.0v to the laser.
as for the resistor value, you need to calculate the gain, a fairly easy equation. The gain is around 100 (as far as I remember at least) so if you need 60mA out, you need 0.6mA (at least) so since R=V/I then R = 3.3/0.0006 or 5500 ohm (unless you are using 5v battery of course) realistically, using a 1k resistor means you will happily flip the switch and not over current and damage the transistor. Anywho, my electronics are a little rusty, so feel free everyone to chime in and correct me.
You can turn the diode around and put it in series with the LED to drop the voltage another .7v to get closer to 3.3v from a 5v supply. The local walmart has laser pointers in the checkout lanes for $2.49. These use 3 button cells so they operate at ~4.5v.
just a quick warning with those: some (not all) of them rely on batteries internal resistance to determine current levels, and pop when used with a higher current (read nimh) battery
My laser diode isn’t particularly sensitive that i know of. i’ve ran it off a single AA battery, and off of the 5v regulated, neither caused any problems, though the 1 AA battery was a bit dim.
I still don’t know what to use for R1 in this particular setup.
And i’ll use any of the npn’s, but if you guys have a suggestion i’m open to it. The 3904’s are the most numerous so i’ll probably use one of those.
Just go.
R1 = ____
Q1 = ____
And i’ll make it. you say 10k ohm, 22kohm, 2.7kohm, 20ohm, what ever you say, i’ll use. What ever works best and has the least power consumption to get the job done.
I really appreciate how helpful and informative you guys are, but sometimes the straight answer is the most useful. At least until i can get a book to learn about this stuff. When i say i don’t know the difference between a 10kohm resister and a 22kohm resister, i mean i don’t know what their effects are. does 22k have more resistance? what does the resistance even do? i have no clue.
I’m the construction worker, i follow the blueprints, the floor plan.
I’m not the home designer.
You say Pipe goes there, i put pipe there. I don’t ask why, or what it’s for.
(I’d probably do well in the military.)
