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7805 Regulator problem for pic16f877A

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furqankaimkhani

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For my pic projects, i used to have a small adaptor giving 12 volts as power supply(max 500 mA).
With that,
I have been using 7805 regulators for PIC projects with 0.33uf on the input and 0.1 uf on the output. With this setting, the smaller projects that are on a single vero board work fine.

But with bigger projects with multiple vero boards and more accessories, i need a bigger power supply.

Can any one help pls. I have a local transformer with 1 amp rating i guess. Is 7805 still valid for this? And i dont know for higher current, which capacitors ii should put on i/o of 7805.
 

For my pic projects, i used to have a small adaptor giving 12 volts as power supply(max 500 mA).
With that,
I have been using 7805 regulators for PIC projects with 0.33uf on the input and 0.1 uf on the output. With this setting, the smaller projects that are on a single vero board work fine.

But with bigger projects with multiple vero boards and more accessories, i need a bigger power supply.

Can any one help pls. I have a local transformer with 1 amp rating i guess. Is 7805 still valid for this? And i dont know for higher current, which capacitors ii should put on i/o of 7805.


Hi,

The caps around a 7805 are the same whatever the current being used.
Also important is to fit each Pic with a 100nf as close as possible across its power pins. - Do the same to any other ic you use.

I never use power components at their maximum rating, at 7805 at 1A will get very hot when dropping 7v across it., even with a large heatsink.

Much easier and cheaper to use 2 or 3 separate power lines each with their own 7805 running at a much lower current.
Connect the 0v lines togther but never connect the +5v lines togther, it does cause problems.

An alternative is the adjustable LM317 which is also cheap but handles up to 1.5 A so you should get 1A out of that with a decent heatsink.

You will probably find a 7812 to provide 12v for things like relays etc very useful. - they should all run ok from that transformer provided you keep an eye on the total load, use a 1A fuse on the transformer output line , something people do not seem to bother with much these days .
 
You can use this ciruit :
5v_supply.gif
Source:http://www.talkingelectronics.com/te_interactive_index.html
 

For my pic projects, i used to have a small adaptor giving 12 volts as power supply(max 500 mA).
With that,
I have been using 7805 regulators for PIC projects with 0.33uf on the input and 0.1 uf on the output. With this setting, the smaller projects that are on a single vero board work fine.

But with bigger projects with multiple vero boards and more accessories, i need a bigger power supply.

Can any one help pls. I have a local transformer with 1 amp rating i guess. Is 7805 still valid for this? And i dont know for higher current, which capacitors ii should put on i/o of 7805.

7805s come in different varities - 7805C can supply 1 Amp, 78L05 --100mA, 78M05 --500mA. LM7805C series is available in an aluminium TO-3 package which will allow slight over 1.0A load current if adequate heat sink is provided.

For multiple vero boards use decoupling capacitor on ech board. A decoupling capacitor is a capacitor used to decouple one part of an electrical network (circuit) from another. Noise caused by other circuit elements is shunted through the capacitor, reducing the effect they have on the rest of the circuit. An alternative name is bypass capacitor as it is used to bypass the power supply or other high impedance component of a circuit.

Juse attach a 0.1mfd capacitor across V CC /GND on each board to try and keep the voltage more constant.
 
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