http://www.kpsec.freeuk.com/index.htm
Here ya go!
Now how do you use a transistor in place of a switch/button?
So I can use this with my Basic Stamp 2?
http://www.makershed.com/ProductDetails.asp?ProductCode=MKAD4
Admin Edit: Changed post title and removed useless posts.
I’m not really sure what the
I’m not really sure what the first link has to do with the question about transistorising the TV-B-Gone, but you’ll need a transistor and a resistor to replace the switch in the TV-B-Gone circuit.
Find yourself a generic NPN transistor with a collector current limit of at least a few hundred mA, and preferably a low VceSAT value. From the transistor’s minimum current gain you can choose a resistor to match it.
The transistor’s collector is connected where the positive switch lead was connected, and the emitter goes where the negative lead was. The base is connected to one of your BS2 outputs via the resistor.
Here’s a simplistic tutorial
Here’s a simplistic tutorial on using transistors as switches
http://www.mayothi.com/transistors.html
This thread confuses me. Not
Transistors require a voltage on the base to pull current through from the collector to emitter, or the other way around.
PNP transistors require a negative (ground) input on their base for their emitter to conduct to the collector (think of a PNP as backwards). NPN transistors require a positive source for the collector to conduct to the emitter.
PNP go from the voltage source to the controller, where NPN Goes from ground to the controller.
Example:
The top part can be considered sourcing the LED, it recieves power constantly and the 555’s low period acts as a ground. (PNP)
The bottom part can be sinking the led, where it recieves a constant ground, and the 555 acts as a voltage source. (NPN)
Simple transistor driving a relay
Simplistic!
Yeah thanks, i just needed something like that!
I know this is quite old,
I know this is quite old, but today i thought about it and i don’t understand why the work like that. What i mean is: if you connect a BS2’s output pin to the base of the transistor which has the collector and emttier connected to another independent circuit, where does the BS2’s current end up? Shouldn’t it get back to its original source? (say through a connection between the BS2’s ground and the other circuit’s ground)
Many circuits will not work
Many circuits will not work unless the grounds are connected between them. Exceptions are those that have been opto-isolated or isolated in some other form. Voltages generally need a reference point, and that is typically ground. Essentially, it means that the above circuit assumes that the transistor ground is also the BS2 ground, in order to work. The relay switch can be isolated completely from the BS2 and transistor.
but i managed to to this
but i managed to to this with an USB mouse (don’t think it is opto-isolated in any way). I just connected collector to the switch’s “anode” and the emitter to the “cathode” and the base to my picaxe without connecting GNDs…how come?
I can understand why this happens with a relay, but in every tutorial i’ve read they say current enters the base and ends up through the emitter.
Want to post the full
Want to post the full circuit? It’s not clear what you have from your description. First you mention a USB mouse, then you say something about a switch that somehow has an anode and a cathode, which sounds more like a diode to me. How is th USB mouse involved? How are you powering the PICAxe?
Here’s the circuit. As you
Here's the circuit. As you can see the two power supplies are isolated from each other. What i don't get is: shouldn't current A (marked in red), given out by the picaxe's batteries get back to them(picaxe's batteries), somehow?
PS: i wrote anode and cathode between commas (") because they aren't actaully anode and cathode. I was just trying to refer to the different contacts on the mouse's switch.
Yes, the small current A you
Yes, the small current A you have marked should have a path back to the PICAxe batteries somewhere, or else not cause the transistor to turn on.
Exactly…but the point is
Exactly…but the point is that it works if i connect it like the picture shows.
How exactly is it supposed
How exactly is it supposed to work? What does the transistor do to the mouse that the switch shown normally did?
Also, what type of
Also, what type of transistor are you using? If it’s a FET type then the circuit posted will work (although not reliably), while if it’s a BJT then the circuit should not work for more than an instant at best.
The circuit i made was
The circuit i made was simply a “fast mouse clicker”. It basically goes high output, pause 100, low output. The mouse’s switch is simply its left mouse button.
And…it’s a BJT. And it works normally.
I too did not expect it to work since it wasn’t a FET, in fact the first thing i did was to connect tie grounds together. But once i untied them it worked. If you want i can take a photo of it.
