I'm using 5v regulator (this one:http://solarbotics.com/products/lm2937/) and it doesn't seem to be working correctly. I'm under the impression that this is how it should work:
On the first of the three prongs, I put the positive (red) wire from a 9v battery port thing
In the middle prong, I put both negative (black) wires.
On the third prong, I put another red wire
A black wire from the middle prong and the red wire from the third prong should, when attached to voltmeter, give 5v. Currently it is giving 9v. I have tried switching the positive wires.
Am I incorrect in any of these assumptions? If not, what am I doing wrong? Basically, how do I get 5v from 9v?
Um… it doesn’t sound like you’re doing anything wrong. Maybe your regulator is busted? They’re pretty tough components, but even the best parts break sometimes. I’d normally suggest checking for shorts or accidental solder bridges, etc, but those would be pretty obvious in this case.
Have you soldered the wires on? Or is this built on a PCB or a breadboard?
Not sure about whether the Not sure about whether the regulator will block current going the wrong way, but it definitely shouldn’t read 9V in both directions… yeah I can’t think of anything that could cause this to happen except a busted regulator. Maybe there’s a more convenient local electronics place you could get some 5V regulators from? Since you’re using 9V supply you don’t need a low-dropout regulator, and the ‘7805’ family of 5V regulators is very common.
I also thought the 10uF cap was for noise filtering, but I have just tried it and the voltage spikes (possibly to 5v?) and then flattens out to 0. I am supposed to attach it in series with the voltmeter in the output circuit, correct?
also, I tried connecting it in parallel, but that just gives 9v still.
wait, should there be a cap wait, should there be a cap on the input circuit too? I have to confess I don’t really understand that diagram. Do all the little arrows go to the ground?
Yes, all the ground points Yes, all the ground points are connected. The ground symbol is a convenient method to illustrate that without having to show all the connections. On some diagrams, this keeps it from getting too ‘busy’.
alright, I think I get it. alright, I think I get it. Still, though, I wired it up exactly like that diagram and still nothing. this is getting pretty frusturating
sorry to double post, but if sorry to double post, but if I get a ‘standard’’ 5v regulator (for example, this one from radioshack: http://www.radioshack.com/product/index.jsp?productId=2062599 ) , do I need capacitors? I’ve pretty much written my first one off as broken.
I’ve never had a problem I’ve never had a problem using a 7805 without smoothing/filtering caps when running off batteries, but I they’re usually a good idea anyway, since they don’t take up much space. Especially useful if you’ve got a noisy power supply (like some wall adaptors can be), sensitive circuit parts (poorly isolated oscillators, radio frequency subcircuits), or circuit components that can generate noise or power spikes (motors and inductive parts are the most common).
alright. thanks! I probably alright. thanks! I probably will use a capacitor, it’s just nice to have to worry about complicated circuit designs and what not… anyway, I’m going to radio shack right now and will see how it works.
