Hello, I just received two new voltage regulators from sparkfun:
upon connecting one of them (I did not connect the second one yet in case I did something wrong) to this circuit:
(the imaged regulator is the old one that does work properly)
that is powered by a AC/DC Adaptor (used be for a house phone I believe) which outputs 9V/600mA.
May I also add that the adapter outputs in reality 10-15V but that shouldn't matter so long its above the dropout voltage of the regulator and below the max (which I believe is 20v).
I measured 10+ voltage from the regulator (practically no change), the regulator heats up too.
Now heres the interesting thing: an older voltage regulator, in the same circuit, gives an output of 4.8 voltage.
My question is this: do I have a defective regulator or did I somehow ruin it? Could the thinness of the new regulator compared to the old one make it less tolerant and as thus doesn't properly regulates the voltage without proper cooling?
Thanks in advanced to anyone who can help me on the matter
Probably have it backwards? Either that or bad regulator.
Also - do you have a cap on input and output? I don't think that's the problem, but you're supposed to have a cap on both input and output.
For future reference, while a photo of a breadboard is nice, make sure we can see everything that we need to. I can't see much of anything from that picture, because the cap blocks my view of the connections, and I don't know which power rail you're applying power to, and which it's supposed to be outputting on (that part is out of the frame).
Remove everything from the circuit until you are left with the regulator, take a good picture of the setup and describe what your measurements are. Make sure you can trace the connections on the photo before you post it. It also helps to post here the markings on the regulator such as brand and part number. You assume the center pin is ground?
liudr:
Remove everything from the circuit until you are left with the regulator, take a good picture of the setup and describe what your measurements are. Make sure you can trace the connections on the photo before you post it. It also helps to post here the markings on the regulator such as brand and part number. You assume the center pin is ground?
Hopefully that's not an assumption, but rather the result of reading the datasheet or googling the part number. It's just a 7805 - he linked to the sparkfun page. Kinda pricy, considering that it's such a poor regulator.
I don't see a capacitor on the regulator output. Some regulators will work like that and some won't. If, as you say, an old regulator works in that circuit you could try adding a capacitor on the output of between 0.1 uF and 10 uF.
Hi everyone, thank you for all the quick replies! Sorry for the bad quality pic, next time i'll provide with a better one.
there are two capacitors both 25V. the front one (connect to the main power supply) is 100 uf and the there is a second one from behind that can't be seen so well because of the bad picture (sorry again) which is 10uf.
this is the datasheet I reviewed for this regulator (same one sparkfun linked on the product page) datasheet
from my understanding, when the label is towards me, the left pin is input, middle ground, and right output. As I did in my circuit.
I will try and bring higher quality pictures as requested once I get back home in an hour or two.
Seeing as my old regulator works just fine, should I test out the other new regulator and see if it works?
from my understanding, when the label is towards me, the left pin is input, middle ground, and right output. As I did in my circuit
Yes, that is correct. Maybe the regulator is bad. Try the other one but only momentarily supply power to it by holding a wire and sticking it into the board and ready to pull out. Have your multimeter measure output as you try this.
I'd actually be surprised if the part is bad. I don't think I've ever seen a bad one or burned-one out. They are thermally protected, so they don't normally die.
Try a 0.1uF ceramic capacitor in parallel with the electrolytic capacitors. Electrolytic capacitors don't "look like" capacitors at high frequencies, and the regulator might be oscillating at a high frequency. (The datasheet shows 0.33 on the input and 0.1 on the output.)
Just for future reference.... It never hurts buy extra of these kinds of common parts and keep them on-hand. I've usually got a few 7905's, 7812's & 7912's, 7815's & 7915's lying around. It makes it easy to swap-out a suspect part when troubleshooting. If two parts give you the same symptom, it's probably a circuit/wiring error. And, if you fry a part or just need another one for something you don't end-up having to order one small part and paying more for shipping than for the part itself.
I have a funny feeling that however it happened, the regulator in the first instance was inserted backwards and internal diode action fed 10V from "out" to "in".
My suggestion would be to try the faulty regulator again, then turn it around and see what happens!
Can't do any more harm after all as long as it is not powering something sensitive.
Perhaps for some reason the ground connection to the regulator hadn't made contact? That would result in about 2 V drop as reported.
That is possible as indeed is any other connection line missing. He was using solder-less breadboard which is a great way of missing real connections. That is why I recommend you avoid it.
Well, solderless breadboard or no, the photo is 100% useless as it is not in focus. I think the rule here is that unless your photo is perfectly focused, just don't bother to post it.
It looks however as if there are (coloured) extensions wired to the regulator rather than plugging it directly into the breadboard, thus multiplying the chance of poor connection by 8.
