# [SOLVED] Voltage Regulator issues



## Saturisk (Jan 2, 2011)

I am using an LD33V (Low-Dropout 3.3v) regulator to drop 7.4v to 3.3v for my portable nintendo system I am working on. I am just having some trouble hooking everything up.
I included my own wiring diagram (Well labels)








It seems as though I'm doing something wrong with my ground. It's not hooked up as I don't want to hurt anything, but when I hook up the 7.4 to the regulator and put the 3.3 on the board the thing turns on, but I don't even have the 7.4 wire from the switch turned on. I check the switch, it's fine, but I don't understand a lot about circuitry.. The diagram itself is how I understood it while I took my Nintendo apart and looked some other websites regarding it.. I just don't know if I'm making a simple error or not.


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## Saturisk (Jan 2, 2011)

*Re: Voltage Regulator issues*

After further review I actually believe it is a problem with the protection circuit I have... I hooked it up after desoldering everything and making sure there was no contact where there shouldn't be, and I plugged it back in and it worked for a mere 10 minutes. When the nintendo didn't come on again I checked the voltage on both the B+ and B- which game 7.4 like it should then I checked on P+ and P- and it showed only .0456 or whatever small number.. I don't know jack about why it would do this.. any pointers?


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## Saturisk (Jan 2, 2011)

*Re: Voltage Regulator issues*

Once again I speak before I think, the protection circuit when overwhelmed amperage wise has a low stand by current release.. So everything't fine I just need a relay to drop my 12v screen's amperage to less than 8 amps.


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## octaneman (May 13, 2009)

*Re: Voltage Regulator issues*

To see what goes where your going to start off by re-making your connections one-by-one because from your diagram I don't see the regulator being grounded anywhere. 

Start off by taking the 7.4v that goes to the input of the switch, then toggle the switch on/off to see if the output side of the switch gives the exact in voltage. 

From the output of the switch take your 7.4v and connect it to the input of the regulator and then connect the ground of the regulator to the pcb's ground or chassis ground. Test the regulator by toggling the on/off switch so the output of the regulator should be 3.3v. 

From your description it is from the output of the regulator the defines when and if the machine turns on. Place the 3.3v output to where it should go the machine should fire up.


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## Saturisk (Jan 2, 2011)

*Re: Voltage Regulator issues*

Well the regulator was grounded in the picture.. top left of the mobo. but i figured out the power problem and got a handle on it. Which is good, I just can't seem to get the video to work... I am using 3 5" TFT LCD Rear View Monitor Night Vision Car Rear View Backup Camera | eBay which is a 9v but im running 7.4. I can get a picture when it's hooked up to my raspberry pi but that's just running the component cable to another component cable. I had to take the component cable apart for this which gets the ground and the component wires separate, correct? From there I put the component into the video part of the mobo and then I just connected the other like a regular ground, but when I hook everything up it doesn't even blink.







just by reading this it told me to ground out the screen too, but I swear I'm making a smal mistake.


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## octaneman (May 13, 2009)

*Re: Voltage Regulator issues*

I saw the specs on the TFT on the link you gave, it runs on 12v with 4 watts and you are only pushing 7.4v thats a ratio of 1.71 that makes a huge difference. Have you thought of running the TFT with an external 12v power but keep the component video wires connected to the mobo ?


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## Saturisk (Jan 2, 2011)

*Re: Voltage Regulator issues*

Well that's the thing. I have an external power source for it if I needed. but I had it hooked up to a 9v power supply and hooked it up to my raspberry pi, and I got a signal. Then I took the same power supply and hooked it up to my nintendo with the yellow wire form the component cable to the video spot and the other cable to the ground of the nintendo. and nothing happens.


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## octaneman (May 13, 2009)

*Re: Voltage Regulator issues*

The mod you've made is to have better resolution right ?


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## Saturisk (Jan 2, 2011)

*Re: Voltage Regulator issues*

I actually just used that picture to base off my diagram.. I am not using a psone screen for it, I'm just hooking up composite directly too the motherboard. In the composite cable there are two cables, which are ground and picture correct?


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## fzabkar (Feb 7, 2010)

*Re: Voltage Regulator issues*

ISTM that the 3.3V linear regulator is destined for failure. I would expect that it would be running very hot, depending on the load current. For example, if the load is 1A, then the power dissipated by the regulator would be around 4 watts.

P = V x I = (7.4 - 3.3) x 1


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## Saturisk (Jan 2, 2011)

*Re: Voltage Regulator issues*

Well that wouldn't prohibit the screen from receiving a composite signal would it? I figured since it would power on the motherboard at a constant rate it would be fine.. I tried getting ahold of another PTH08080was voltage regulator from Ti but apparently it was one per customer on the samples.  and I have no money to purchase another... I still don't think that would be the problem...


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## Saturisk (Jan 2, 2011)

*Re: Voltage Regulator issues*

Sorry to have not replied further. But Fzabkar are you saying that the power going through the regulator (which is about 4 watts) is not enough to run the board and supply enough current to give the board the ability to run the image?

Also, when you did ohms law why did you subtract 7.4 from 3.3 (I'm still confused on ohms law and what to do with resistance and all that.)


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## [email protected] (Nov 16, 2004)

*Re: Voltage Regulator issues*

He subtracted those two voltages to get the voltage ACROSS the regulator. The 7.4V is the input voltage, 3.3V is the output voltage after regulation by the device. That value, 4.1V, when multiplied by the current through the device (1amp) gives the Wattage, 4.1 Watt, that needs to be dissipated by the device as heat.

If the device becomes too hot, it will throttle the output voltage down to reduce die temperature. If the output current is higher then the 1 amp it will heat up even faster.

Ohms law is really quite simple. V=IXR & I=V/R & R=V/I. Power is related, eg, P=VXI; P=I^2XR; P=V^2/R.

Power (Watts) is an effect of voltage, resistance, and current. It doesn't flow. Current flows. Voltage is a potential that causes that flow (like water pressure), and then there is Resistance to that flow (like a restriction in a water pipe).

Here's a site that will help with your calculations: Ohm's Law Calculator


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## Saturisk (Jan 2, 2011)

*Re: Voltage Regulator issues*

So how is that compared to using a texas instruments voltage regulator such as the PTH08080WAS that is used on the ones I always see rather than my LDO regulator? Or how would I be able to calculate the current of it?


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## [email protected] (Nov 16, 2004)

*Re: Voltage Regulator issues*

Do you mean, how does the LD33V compare to the TI PTH08080WAS? 

There is a huge difference. The LD33 is rated at only 800mA (0.8 Amp), where the TI part is rated at 2.25Amp! The LD is an analog device, the TI is a digital device. Both will produce noise, but the TI will produce 10-100 times the noise of the LD so....it will need lots of output filtering.

The LD33 will need a heat sink...in fact, I believe that the Nintendo will draw 1.2Amp, so it's probably going into shutdown after a minute or two. Even with a heatsink.

To find the rated current of whichever device you choose as a power regulator, just google the part number. In the list of links will be one or two that are PDF's. That's usually the data sheet for the device. And of course you can go to Mouser Electronics, search for the device and there will be a data sheet available.

As far as finding the current requirements of the Nintendo go, if you have a digital multimeter, there should be a 10Amp current setting. Put that in series with a lead to the 3.3V input from a known good 3.3V source and measure the current. Then you can, using data sheets of devices, figure out what type device you need.

The rule-of-thumb for electronic devices ratings is always TWICE what is required. So if you need a 1amp regulator, you buy a 2A. If you need a 1/2Watt device, you buy a 1Watt. If you calculate you need a 100uF cap, you buy a 200uF...and so on.


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## Saturisk (Jan 2, 2011)

*Re: Voltage Regulator issues*

Okay I see.. I guess I haven't fully grasped the concept of current vs voltage.. I just figured it was 3.3v so it would work.. That makes sense though. Thank you for your help! I will try to work something out knowing this. Thanks again!


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## [email protected] (Nov 16, 2004)

You are welcome. As an aside, I spent several years as an electronic engineer reverse engineering toys...like Nintendos. Kinda fun. But many times I'd run into toys that were so poorly made or designed, they were almost guaranteed to fail sooner rather then later. Not the Nintendos though. Those were pretty well designed and produced. I had fun upgrading them though.

Anyway, keep on it. You'll figure it out.


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