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[help] Getting pure DC current

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hi...

I have a 6v DC = 4 x 1.5V AA battery that generate 1.2V AC........ so how do we totally eliminate those AC current?

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I have a 6v DC = 4 x 1.5V AA battery that generate 1.2V AC........ so how do we totally eliminate those AC current?

What frequency? A filter capacitor will reduce it if the frequency isn't too low.

What current? AA cells won't supply much current.

What battery chemistry? Carbon-zinc and "heavy-duty" cells are lousy. Fresh alkaline cells have an internal resistance totalling 1 ohm so 1A will drop 1V. As they run down the internal resistance rises which causes more ripple.

You could use a voltage regulator to reduce the ripple to nearly nothing. Also a 6V battery drops to 4V as it ages but if you have a 12V battery then it can drop to 8V and a 6V regulator will still regulate.
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i'm using alkaline cell maybe is 0.12 ACV......

0.1uf polarized capacitor will do?

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0.1uf polarized capacitor will do?

A 0.1uF capacitor is much too small as a supply bypass capacitor. With a new battery that has a 1 ohm internal resistance it will reduce supply ripple to half at 1.6Mhz. 1000uF will reduce supply ripple to half at 160Hz.

What circuit do you have that has a high output current and a low amount of ripple rejection?
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well I mearsure the 4 x 1.5V AA everday super heavy with digital multimeter:

1. when I switch it to DCV 200 mode it show 05.8

2. when I switch it to ACV 200 mode it show 12.2

3. sorry I don't have oscillator therefore i don't know the frequency :(

I need 1000uf... those are super capacitor........?

btw, i use it for PIC project....

Thanks

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well I mearsure the 4 x 1.5V AA everday super heavy with digital multimeter:

Super Heavy Duty cells are cheap garbage, use alkaline cells.

1. when I switch it to DCV 200 mode it show 05.8

Then the cells are not new or can't pass the current.

2. when I switch it to ACV 200 mode it show 12.2

12.2VAC is impossible from a 6V battery. Your meter is picking up interference.

3. sorry I don't have oscillator therefore i don't know the frequency

It doesn't matter because something is wrong with the meter or the way it is connected.

I need 1000uf... those are super capacitor........?

1000uF is an ordinary cheap little electrolytic capacitor that I use as a battery bypass for audio battery powered projects. I use a 100uF cap as a battery bypass cap for most other circuits.
The value of a supercap is measured in its number of Farads. 10,000 times la higher value than 1000uF.
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I teasted o.1, 1 and 10 uf polarized capacitor as bypass capacitor but it seems not working

The reason I'm asking about pure DC is because my PIC microcontroller get heat up so fast and damn hot............ and I have fried few of my PIC :(

Thanks
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Your microcontroller should work fine on a supply of 5.8V, and a small bypass capacitor.
It would get too hot if it had floating inputs, a clock frequency much too high or if it is driving a short.
Attach your schematic for us to see what is wrong.

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Just for clarification, why would one want to measure the DC voltage of a battery on the AC mode of a VOM?

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The battery has an internal resistance. Therefore its voltage fluctuates (AC) with changes in load current. A huge supply bypass capacitor will help but a higher voltage and a voltage regulator IC that has an extremely small internal resistance will fix the fluctuations.

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Thank you, audio

A very excellent explanation of ripple effect and the almost universal necessity of using bypass capacitors in many circuits.

Failed to answer my question, though.

AllVol

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Hi Allvol,
I don't know why Draggy measured ripple on his battery's voltage and I don't know its cause or its frequency. Sometimes his ripple's amplitude is impossibly huge. I think his meter is playing tricks on him.

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draggy,
I am pretty sure 6 volts is a maximum value for your PIC. If your batteries are exceeding this and your meter is not showing it, this is not good for your micro. Check your spec sheet for more specifics on this.

In most cases that I have seen, where a PIC gets hot, it is due to misconnection or the sink/source current of the pins being exceeded. The port pins are ok with being shorted, but you cannot sink or source more than 10 to 25 mA. Exact amount depends upon your micro. Again, look at your spec sheet. When you run the PIC in a breadboard with only the crystal circuit and power supply attached, does it still get hot? Members reading your posts can only make a guess, so it would be beneficial if you could show a schematic of your circuit as requested in a previous post.

MP

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well I mearsure the 4 x 1.5V AA everday super heavy with digital multimeter:

1. when I switch it to DCV 200 mode it show 05.8

2. when I switch it to ACV 200 mode it show 12.2

My point is that Draggy apparently is using his meter wrongly in an attempt to find the "AC" that is hampering his PIC operation.
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lastest update:

ok, this time I put 5V DC regulator(LM7805C - V) when i switch on the PIC microcontroller, the regulator heat up as if can cook an egg  then later come the PIC microcontroller turn to heat up...... :(

Thanks

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Of course they get hot: your power supply connections are backwards!

You should download the datasheets of the microcontroller and the display. I get datasheets from www.datasheetarchive.com .

Why post your schematic as a 1.33MB huge bitmap on another site, when you can change its file type to a very small size PNG by using MS Paint program then attach it here like I have done?

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By the way, you should also download the datasheet for the 7805 regulator. Its minimum input voltage is about 7V to 8V. Its output voltage will be about 4V and is not regulated with a 5.8V input.
Also it needs a capacitor on its input and a capacitor on its output is recommended in the datasheet.

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:-[ thanks man that was a big wake up call  :-X

0.22uf on the input and 0.1uf output :)

Thanks a lot

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