Continue to Site

Welcome to

Welcome to our site! is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Help with wiring a voltage regulator

Not open for further replies.


Newbie level 6
Oct 5, 2009
Reaction score
Trophy points
Activity points
Hello and TIA!

I'm trying to power a wireless camera off of a battery pack. But in doing so I've found out that it goes through batteries pretty quickly and so I started learning about them. So I am trying to use rechargeable batteries but have need of reducing the voltage.

The camera takes 650 mA max at 5v.

The battery pack runs off of AA 1.2v batteries.

I picked up a 6v 1A voltage regulator.

I tried different ways of wiring it, and one or two ways work :p ... but the when it does work the VR gets really warm/hot and just sucks up battery power extremely fast negating having 8 1.2v batteries Vs. 4AA 1.5v batteries.

I have a drawing and some notes of what i've found out. So any help would be appreciated.
Also I've read t hat having a capacitor isn't necessary, but helps in stabilizing the voltage. What kind of capacitor would I be able to use for this purpose?

When I originally picked up the voltage regulator it was all I could find, I've since then picked up a 5v 1A VR.

Although I didn't bring the notes with the readings I did take them with a multimeter and everything looked ok (correct voltage and decent mA's). The only other problem I saw though was a pretty big drop in mA. I would have though the VR would out put 1A since that was it's max (or close to it).

Thank you

##### Updated info 10/06 #####

These are pictures of the voltage regulators.

These are pictures of batteries.

The rechargeable batteries have the following output (at almost full capacity charge):
8 AA 1850 mAh nimh = 10.6 V
8 AA 1850 mAh nimh = 1.74 mA

4 AA 1850 mAh nimh = 5.25 V
4 AA 1850 mAh nimh = 660 mA


You can get small ones, for your usage, and you can buy these from RS (open-frame smps)

or you can design your own like from or etc.

or by the babani book $5 on power supplies which tells you about voltage regs.

Fistly, for a linear voltage regulator, the input and output currents should be almost the same (the difference is the consumption of the VR itself). Your jpg file shows that something is going wrong.
2- Any linear VR needs some voltage drop across it to run properly (eg. 2,5V for a LM7805 or less for a LDO type).
3- The voltage across the regulator multiplied by the current defines the amount of power dissipated by the device (and also the size of the heatsink you´ll need).
4- 1.25A seems to be too much for AA batteries and this current doesn´t match the spec. of the camera. One possible cause is it is oscillating because you didn´t place capacitors at the input and output pins to ground (read the VR´s datasheet to see the recomended values).
5- Even using a SMPS (recomended) your batteries will last for a few hours. Your circuit#2 may also work if rightly decoupled and if an output of about 4.5V is accepted near the batteries end of life.

Ah ok thanks for the info. I have started looking into what SMPS are (no idea, never heard/knew of them).

The VR I got didn't have any information except what the pins were for.

1) so the voltage should be about 5v going INTO the voltage regulator?

2) how do i make the voltage drop?

3) so 9.6v * 1250 = 12000? so that's how much power it's consuming and why it gets hot/kills batteries so fast?

4) Well i'm using rechargeable batteries. I found out that alkaline AA's are 1.5v and rechargeable are 1.2v. Their capacities are about 1850 (originally) but have been around for a while.

5) I will continue to look into SMPS.

I will take more readings and post them up maybe to help clarify some of the things i'm doing wrong.

As of right now the camera functions with infrared capability (when there isn't enough power the IR turns off and only transmits in "color mode").

Thanks for the info!

You forgot to tell us the spec's for your AA rechargeable cells. Are they old low-capacity Ni-Cads or high capacity Ni-MH?

Name-brand Ni-MH AA cells have a 2500mAh rating and can supply 650mA for 3.8 hours.

Using the same size battery (AA cells) but with more of them and a regulator does not reduce the current so the life of each charge will be nearly the same as before.

1- 5V should be the output voltage of the VR.
2-The voltage drop is inherent to the device. You can´t change it. What you need is a minimum input voltage equal to the output plus Vdrop.
3-When calculating dissipated power the voltage to be taken is the difference between input and output (not total input voltage)
4- 1.5V is the fully charged voltage for alkaline batteries. They drop to about 1.2V when discharged. Also, 1.2V is the discharged voltage for NiCd or NiMe batteries. Their fully charged voltage is about 1.45V.
5- A SMPS would be a good choice.

The rechargeable's i'm using are ni-mh 1850 mAh. (8 of these - used for i'd say 2 years now but with a charger that conditions them)

Oh, so if the voltage regulator doesn't reduce the current, couldn't I use a resistor for that?

2) So if I have a v drop of 1 volt, in order to achieve say 5 volts then the input has to be 6 volts correct?

Yeah i'm looking into SMPS but it's not making much sense at this point haha

I've found this and am trying to understand it

If you guys could point me towards something that could help my understanding of this i would appreciate it.

thank you

Again, the large input current you have measured (1.25A) is due to a malfunction. The input and output voltages of a linear regulator are almost equal. If your VR is of a LDO type witha 1V voltage drop then you´ll need a minimum of 6V input to obtain a regulated 5V output.
I suggest: **broken link removed**


    Points: 2
    Helpful Answer Positive Rating
ok thank you very much! I will check everything when I get home and verify before I do anything else :p

Thank you for the link and for your time guys.

Which regulator are you using? Its datasheet tells you its minimum input voltage for it to regulate, probably it is 7.5V. The minimum input voltage is its output voltage plus its dropout voltage.

Why are you using extra battery cells and a voltage regulator? The life of each charge will be about the same as with 4 battery cells.

I got a VR that says its a 6v 1A VR. It has 3 pins, v-in, g, and v-out. That's pretty much all there is to it. I got it from Fry's Electronics so it doesn't come with anything else than that.

This is the situation, someone slashed the tires on my motorcycle. I park it in my apartment buildings open garage - open access to anyone. So I have a wireless security camera that barely transmits the signal over the distance. Unfortunately, there are no outlets to power the camera. So I hooked it up to a 4 AA alkaline battery pack and it works, but only lasts about 7 hours.

So, I figured that could be acceptable and I could switch batteries a few times a day. But AA ni-mh rechargeable batteries can't power the camera which takes 650mA when infrared is on. So, then I got a 8 AA battery holder and then found out that it's too much voltage for the camera. So I thought a voltage regulator could help with that and although circuit #2 does do that, it doesn't extend the life of the battery pack to 2 x 4 AA's. lol

So I'm learning as I go and trying to make sense of it all.

What voltage and what current does the infrared use?

You could use a low power PIR motion detector to switch a transistor that turns on the camera and infrared. Then the battery will last a long time unless there are many people coming and going.

Maybe your tires were slashed because your motorcycle is too noisy. I would like to blow up a few extremely noisy motorcycles that make a racket near my home.

The camera doesn't specify, only says it takes 5v 650 mA max.

Right now the camera is on as long as it's connected to the battery and it's connected wirelessly to a DVR that records on motion. So if there was another motion trigger involved, there would be a greater delay to start recording.

In regard to your comment, my motorcycle doesn't have a loud exhaust. It actually has the stock exhaust. If you want to know what it looks like check out this picture 01-17-08.JPG

You didn't tell, what's actually the allowed voltage for the camera. A 5V specification suggests a tight range that doesn't allow much tolerance, e.g. +/- 5% (4.75 - 5.25 V). This kind of devices is intended for operation with a regulated 5V wall adaptor. Luckily, it can work with four rechargable batteries. In this case, using a battery pack of 4 considerable larger cells (Sub-C,C, D with 3 - 9 Ah) would be the most simple solution.

As you already found out, a linear voltage regulator doesn't reduce the current consumption. A switched mode supply however does. There are e.g. small 3-pin modules replacing a linear regulator, but not at Fry's, I guess. But you need more battery capacity anyway, and 4-cell NiMH should fit.

Although Fry's has most likely no datasheets for their devices, all ICs are from NTE, a reseller. Your regulator is NTE-962, and it has a datasheet, but rather scanty. If you need more information, you can refer to a similar original manufacturer's type as 7806.

California has a max noise level law for motorcycles. But it was written by a little school kid (or a noisy motorcycle rider) because its rating is 80dBA. The "A" filter severely cuts low frequencies because it is usually used to measure low level background noise and our hearing is not sensitive to low level low frequencies.

The BLAT, BLAT, BLAT noise from a motorcycle exhaust pipes without any sort of muffler is high level low frequencies similar to gun blasts.

I've updated the first post with some more information and values regarding my batteries. I also noticed that I had in other use a monster cell that was "high capacity alkaline" and it claimed to have 2850 mAh... if that is high capacity, then the 2500 mAh nimh would work just as well right?

FvM: When I had tried to use the rechargeable batteries the camera wouldn't even power on. I didn't have the multi meter at that point so I couldn't tell you what the readings are. So I haven't tried since then (maybe they just needed to be conditioned?)

But I have updated the values in my first post. It looks like 4 rechargeable batteries should work... BUT I forgot to grab the camera on my way out! So I will try this when I get home later today.

I would LOVE to use rechargeable D cells but I figured since I couldn't use AA I wouldn't be able to use D. Where could I get some decent D's at a decent price? The few places I've seen with D's are VERY expensive.

You were correct about the regulator being NTE-962. I did end up getting a 5v, 1A regulator from radio shack since I saw they had it, but now I know that isn't going to be the only thing I need.

Thanks for the info on finding the data sheet, I found this but I think it's more than what I need at this point...

The problem of using an in part inapproriate "A" weighting isn't specific to traffic noise regulations. However, the 80 dBA value is an emission limit. The respective immision level (what you hear in your house) is considerably lower and not too far from ideal "A" weighting conditions.

Ok so I looked up the info for the LM2575 SMPS. I have a few questions for what I need to get in order to build a device powered by several rechargeable batteries with an output of 5v and max 1A of current.

My questions are based off of this drawing:

A) This is going to be the battery power supply. It could be from 4 nimh AA 1.2v to D 1.2v cells, 6v to 20v max input.

B) This capacitor should be 100 micro farad for my needs?

c) I think this is a diode, but don't know much else. If I guess correctly, it should be the diode # 1N5819 (should have some sort of set measurement).

D) This is a 330 micro henry inductor? What does L1 stand for?

E) This capacitor should be a 330 micro farad cap?

F) And finally, would it be ok to ground everything to the project box itself wherever references to ground are made?

So, would those values be enough for my needs?

A buddy here at work gave me an idea, could I use the power converter that came with the camera itself? For example, since it would already reduce the voltage and current to 5v, 650 mA, could I hook it up to 8 D batteries?

But my next question is, would it be the same problem as the previous voltage regulator where it makes no difference if its 4 or 16 batteries as that the current will be consumed at the same rate and the unused voltage turned into heat?

thank you!

The minimum input to the LM2575 5v power supply circuit is 7V that you do not have. Your 4.8V or 6V battery will drop to 4V before it is dead.

Oh, yes that is correct. I should have specified that if I don't use the smps, then I can use 4 AA nimh 1.2v batteries, but otherwise 7v is the minimum input for the smps...

So I can use say 8, 16 or 32 1.2/1.5 v batteries to power the device and it would be fine. (Since the max is 7-40v).

What about my understanding of the schematic, are my components correct? I'm having trouble matching up D1 (C). Not sure if it's a a Zener or Schottky type diode.


Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to