Want to power up my programmer

[shaiqbashir]

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Hi guys!

i want to build a simple PIC programmer that requires 13.5 V. This can be to about 14-16V. And it also needs regulated +5V at some of its pins.

The diagram above shown is the power supply setup used for this programmer. There are two power solutions available. Either we connect two 9V batteries, or we connect AC supply to it. You can see the AC jack in in the diagram. Then we have a bridge with us. I want to know that does this socket requires to connect 220V AC supply to it and then the bridge will rectify it OR we should use an adapter that should be able to convert 220V AC supply to somewhat 14V or 16V?

What should we do to power this circuit.

Actually i have never used bridge before. If i go to the market,  what specifications should i tell to the shopkeeper to purchase a bridge for the above circuit. I mean is there any voltage current requirement.??


Secondly, please look at the batteries connections, do u think that these are correctly connected.

im saying this because i see + side connected to the ground in the above diagram.

Thanks in advance!

[audioguru]

Hi Shaiq,
The LM317 needs a minimum input voltage of 3V more than its output to regulate properly. So the circuit needs a minimum input voltage of 16.5V.
Two 9V batteries have a voltage that drops to 6V each as they run down which is too low for the LM317. Rechargable 9V batteries are only 7.2V each when fully charged, which is also too low.
220VAC would instantly blow-up the circuit because it is way too high.

You need batteries that give a total of 16.5V or more during their entire life, or a transformer with a peak voltage of 16.5V plus 1.5V for the bridge rectifier. A 13VAC to 15VAC transformer would be fine.
The 100uF filter capacitor's value seems too small unless the circuit's current is very low. I would use at least 1000uF.
Purchase a rectifier bridge with at least 50V and 1A ratings.
Your battery symbols have their polarities backwards.

[MNA]

Hi Shaiqbashir,
am waiting for your site to be constructed :)

[MP]

Shaiqbashir,
Where do you need 13 volts in your circuit? You only need the final conversion to 5 VDC for the micro. Unless there is more to the circuit that you have left out, you could simplify this and just use a 5VDC conversion. Regulate a 9 volt battery down to 5. In this case, forget the LM317.

MP

[indulis]

Have you considered a DC solution with one 9VDC source, a 5V regulator and a 555 based voltage doubler? You'll only need the higher voltage when burning the PIC and it range is pretty wide so it wouldn't have to be all that well regulated.

[shaiqbashir]

Hi guys!

sorry for late replying, actually my net was havign some problems.

First of all, im very thankful to All of u for taking interest in my question and providing me lots of precious replies.

There have been some questions which are asked to me in return. I would like to answer them now:

Where do you need 13 volts in your circuit?

Well! i need it as a Vcc for my transistor 2N3906

am waiting for your site to be constructed

Thank you very Much MNA.

Now, what im thinking here is that instead of going for a 13VAC to 15VAC transformer directly, why not i use a simple AC adapter that can provide me around 14V DC and 500mA of current. Then i think there would be no need of using this BRIDGE. WHat do u sayy????

[shaiqbashir]

thanks zeppelin!

now tell me one thing!

if i measure the output voltage of an adapter, and i found it to be 17VDC. then may i use it then???

what is the max voltage input i can give to the circuit???

[audioguru]

Hi Shaiq,
The output voltage of a cheap unregulated adapter changes with its amount of load.
The max input voltage to an LM317 is more than 40V. But then it gets hot which might limit your circuit's max input voltage.

[MP]

How about the rest of the circuit? There is no transistor in the diagram you have posted. How can anyone tell you what you need when they do not see all of the circuit? What is the current consumption of your circuit?

MP