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Maccabee
Joined: 12 Jun 2006
Posts: 6
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 Posted: Mon Jun 12, 2006 5:57 pm Post subject: Programmer doubt |
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Im a newbie in microcontrollers.I saw the programmer circuit you recommended in your site,and almost finished assembling it in a common circuit board.I ve no past experience with electronics much.My friend said that if you made a mistake in ur circuit,it will draw more current frm the serial port and cause damage to my PC is it rit? Shall i take any percaution ?PLZ help me.
Also another pblm is I ve used higher value capacitance in the circuit instead of nf and pf .Will it matter much?? |
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KC
Joined: 05 May 2006
Posts: 99
Location: Victoria BC Canada
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| Posted: Tue Jun 13, 2006 3:50 am Post subject: |
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| Quote: | | My friend said that if you made a mistake in ur circuit,it will draw more current frm the serial port and cause damage to my PC is it rit? |
He is right, you can damage your computer if you say, wire the 13V line into the parallel port. So be carefull and double check everything twice before applying power and plugging it into your computer. If you want to tripple check then use a voltmeter to check that the voltages on the computer plug are 5V or less.
| Quote: | | Also another pblm is I ve used higher value capacitance in the circuit instead of nf and pf .Will it matter much?? |
It depends on where you subbed the values. So tell us exactly what circuit you built and which components you subbed.
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KC |
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Maccabee
Joined: 12 Jun 2006
Posts: 6
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| Posted: Tue Jun 13, 2006 4:08 pm Post subject: |
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Circuit i used is from http://www.lpilsley.co.uk/pdf/p16pro40.pdf
I ve some other doubts also in the above circuit
1.Can i apply a 15V DC at input to get the programmer work?
2.I made the circuit to program PIC16F628 so used only an 18 pin socket
with connections pin 9 on pin 20 as said in ckt.hope its rit,is it?
3.Values i changed are C2,C1 100nF and C4 300pF with .01microF
I think to use a 15Vdc at i/p so I hope this wont cause a trouble ,will it?
4.
| Quote: |
If you want to tripple check then use a voltmeter to check that the voltages on the computer plug are 5V or less. |
Do you mean that before connecting my ckt's male D plug(25pins) to PC that i should power it on and check the 25 pins voltages??
5.Is the only way to cause damage to computer is getting a 5V above at the pins in this circuit??
6.Just for knowing,what kind of damage will a faulty ckt can cause to computer?
Thanks |
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Nigel Goodwin
Site Admin
Joined: 03 May 2006
Posts: 135
Location: Lower Pilsley, North Derbyshire
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| Posted: Tue Jun 13, 2006 6:43 pm Post subject: |
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15V DC is too low, it's not enough headroom to feed the regulator.
Connecting things wrong to the parallel port can blow the parallel port, which as it's usually built on the motherboard isn't good!. |
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KC
Joined: 05 May 2006
Posts: 99
Location: Victoria BC Canada
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| Posted: Wed Jun 14, 2006 3:32 am Post subject: |
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| Quote: | | 1.Can i apply a 15V DC at input to get the programmer work? |
Like Nigel mentioned, you need at least 16V. But note that most Wall Wart adapters put out more than their rated voltage when not loaded at 100%. So.... A 15V Wall Wart will work because it'll probably put out 18V or more when lightly loaded by a circuit like the PIC programmer
| Quote: | I made the circuit to program PIC16F628 so used only an 18 pin socket
with connections pin 9 on pin 20 as said in ckt.hope its rit,is it? |
This will mean the 18 pin socket is wired to the lower connections where the ZIF would have been installed:
ZIF-->18pin socket
15-->4
16-->5
23-->12
24-->13
25-->14
| Quote: | | Values i changed are C2,C1 100nF and C4 300pF with .01microF |
C1 & C2 should be OK. C4, while experimental, should be as close to 300pf as possible. Try between 200-400pf for starters. 0.01Uf is equal to 10,000pf Way too much!
| Quote: | | Do you mean that before connecting my ckt's male D plug(25pins) to PC that i should power it on and check the 25 pins voltages?? |
Yes.
| Quote: | | Is the only way to cause damage to computer is getting a 5V above at the pins in this circuit?? |
Most ports will tolerate a short to ground with no damage. You could check for this also with an ohm meter with the power off to the cicuit. Anything higher than 200 ohms should be perfectly safe. You can also check for shorts between adjacent pins which is a common fault for beginner solder jobs.
| Quote: | | Just for knowing,what kind of damage will a faulty ckt can cause to computer? |
Depending on the voltage applied, design of the port, anything from just damaging the parallel port to total destruction of the system. So be carefull and measure those pins if you are not 100% sure what you are doing.
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KC |
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Maccabee
Joined: 12 Jun 2006
Posts: 6
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| Posted: Wed Jun 14, 2006 3:52 pm Post subject: |
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thank you very much.
I ve checked my circuit by giving it a 19.4 V DC supply at input.All the LEDs lights up.
Is that fine?
When I checked the port pins all except the 10th pin shows voltages of range 1.2,1.35 etc.
The 10th pin gives a voltage of 5.53V Is it problamatic?
If so plz tell me what should i do?
| Quote: | | Most ports will tolerate a short to ground with no damage. You could check for this also with an ohm meter with the power off to the cicuit. Anything higher than 200 ohms should be perfectly safe. You can also check for shorts between adjacent pins which is a common fault for beginner solder jobs |
I ve shorted 18-25 pins of the port and connceted it to the circuits ground.What do you mean by "200 ohms"where should i get this much resistace ?plz make it clear to me. |
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