Pallen33

I've got a feeling this might be far too simple, but just wondering if anyone could help me with a little problem I have. I have a 9 volt DC supply voltage (battery) and just simply want to reduce this down to about 5 volts (or less, not too critical). I've read about voltage regulators, but really know nothing about them and how simple it would be to include one in a circuit- what's the simplest solution to reduce the voltage, without mentioning too many weird and complicated sounding components! thanks a lot :roll:

grrr_arrghh

voltage regulators are EXTRMELY simple.

they only have three legs!!

connect a 78L05 as shown below (in the pic called 'reg.gif')

assuming you don't need huge ammouts of current, you won't need a heatsink or anything fancy.

If you really wanted to, you could make a potential divider instead - see the green coloured picture, but the regulator is better because it can cope with changes in the input voltage.

Attached Images

	div.gif (1.4 KB, 1000 views)
	reg.gif (1.4 KB, 1002 views)

bmcculla

One more thing on regulators: You should put a capcitor from the input to ground and from the output to ground (make sure you connect the - side to ground). These two capacitors will make the regulator work better and avoid any potential problems. About 10uF should be good. Regulators are probably the easiest IC out there - well worth learing how to use and there's a regulator in almost every electronics product out there.

Brent

grrr_arrghh

true, I was just trying to keep it as simple as possible, and there shouldn't be too many probs, and he/she is running it from a PP3

Nigel Goodwin

Yes, but it is very important to fit the capacitors!.

If Pallen33 looks at the hardware processor boards used in my PIC tutorials they all use a 5V regulator from a 9V battery.

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PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

Pallen33

Thanks everyone, really appreciated and I think I'm starting to understand it now. Just a couple of quick further questions which I've thought of:
1) Would it be possible to go down to any other voltage from a 9 volt battery apart from 5 volts? Ideally I need 4.5v so there is still a chance that 5v might be too much, but it should hopefully be ok (haven't had chance to try it yet unfortunately)
2) Concerning the issue of capacitors (don't want to stir up trouble or anything!) what is the benefit of putting them in the circuit and have I understood it correctly with the adapted diagram below (not sure on symbol for capacitor!)? Also bmcculla, when you said "make sure you connect the - side to ground" were you talking about the capacitors, and if so, how do you tell which side is the -'ive ? (sorry for embarassing level of knowledge).... I understand that adding capacitors might not be absolutely necessary, but I might as well learn about how they would work in this circuit all the same. Really appreciating all this help....by just searching on the web I was getting nowhere for quite a while!! Thanks.

Attached Images

circuit_118.gif (1.8 KB, 952 views)

TKS

well i have also a sheme whit a pic from every range running whit out caps....


but the best reason could be that it simple keeps working because the i supply already a good voltage soow it is very difficult to say if it is nececary in your circuit..

another point wy not do it to be sure..???

the - side is 1 leg of the think.. if you use the big onse that mount vertical..they have a colour common blue or grey..and then you see the - side nearby one leg..don't have a cam but will do it one day..

the simbol of a capp looks like a battery,,,and the values are in uF common soow if you can search for a sheme you will find fast one..

greetz,

Walter

Nigel Goodwin

You 'might' be lucky without capacitors, but all manufacturers state they are essential - I certainly wouldn't build a project without them. Unless you have access to a scope, and can check for instability, I wouldn't advise you to either - even then, you are only checking under a limited range of circumstances, for the cost of two cheap capacitors you should always fit them!.

As for the negative side of a capacitor, they are clearly marked with their polarity, usually with a large white stripe with negative signs printed on it. The positive leg is usually longer as well. This only applies to electrolytic capacitors, smaller capacitors are usually non-electrolytic and non-polarised.

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TKS

thats what i mentioned to say..

TKS

Pallen33

Ok, I agree that as you say you might as well add the capacitors because don't exactly cost much. Just to check, is my circuit diagram correct? (even if it is a touch on the amateur side!)... heading for maplin in a bit to get the components so just want to make sure I've got the right end of the stick...

Nigel Goodwin

Yes it's fine, if you look at my tutorial diagrams (as I mentioned previously) they use a 7805 off a 9V battery, complete with capacitors.

BTW, I forgot to ask previously, you mention you would really like 4.5V, what is it actually for?.

__________________
PIC programmer software, and PIC Tutorials at:
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TKS

Don't answer...he wants to steal your idea..!!

:lol: :lol: :lol:

TKS

Pallen33

Cheers nigel. If I'm totally honest didn't actually check those links before because thought they might refer to stuff out of my league, but I'll have a look now...

What's it for...hmm, interesting question. It's actually an invention so can't actually go into any kind of detail, but what I can tell you is that I'm using one of those remote doorbells as the basis of the design. The doorbell ringer conventionally just runs on 2 AA batteries (i.e 3v) but it I've had it running up to 4.5v without a problem. The thing is I need it to run from a source which will be around 9v, although the exact size of the battery could be a bit less or a bit more, probably somewhere between 7 and 10 volts (sorry for the vagueness, but difficult to explain without going into details). Presumably from what people have been saying, the regulator should produce a reliable output of 5v (or whatever) no matter what the battery size is (within reason). I was just intrigued as to whether you can get regulators which produce a voltage lower than 5v, although in my case 5v should probably be ok.

grrr_arrghh

if maplin is your local, then have a look at http://www.maplin.co.uk/products/mod...539&Products=1, it is variable regulator, so you could get exactly what voltage you want, provided the input voltage is several volts higher than the output voltage that you want.

Tim

Pallen33

Cheers Tim, I appreciate some specific component advice because I generally feel quite at a loss when I go to Maplin. One question which again might be stupid, how do you vary what output voltage you get? Is it just dependent on what you put in (i.e you get 75% out of whatever you put in), or can you actually vary it even with the same input voltage?
Paul