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switching electronic appliances using pc

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nightcatz said:
it is working exactly the same way as u have told it .....but it is giving just 4.5v

hi,
Can you check the voltage on all pins 2 thru 9 , using pin 18 as Gnd/0V.
Use the program to switch the pins ON/OFF

I will have to sign off for today.

Eric
 
thanks for ur time dude ...even its getting late for me its 11.20 pm here in India...it is almost same for all the pins it is between 4.4 to 4.6v
 
nightcatz said:
gayan....where should i keep the back emf proection diode,can utell me how should i choose the relay according to the component ...pls explain

A RELAY is an Electrically Operated Switch. The Relay allows one circuit to switch a second circuit which can be completely separate from the first.
This is happening when the Current flowing through the coil of the relay creates a magnetic field which moving a lever and changes the switch contacts.

When choosing a RELAY these basic things are very important.

* Coil voltage
* Coil resistance
* Switch ratings

You can see the coil voltage it’s printed on the relay.
You can measure the coil resistance in the relay by the multimeter.
Let say you choose a 5V relay & its resistance showed you 400 ohms.

According to the ohm’s law you can calculate the current required to the coil.
5/400 = 0.0125 A
So the relay driving circuit must provide these requirements.

Regarding switch rating its better you choose big values for the safety matters.
The switch rating is also printed on the relay.
Ex: 230V/10A …..It means it can handle 10A load by the 230V AC mains.

Also there are some different kinds of relays
SPDT, DPDT, Reed relays etc…..

To control one application or two you can use a SPDT relay.
The back EMF protection diode is in the correct place in your picture.
 
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Gayan Soyza said:
Remove the OPTOCOUPLER & give the 470 ohm to the positive supply of the 6V rail & see whether you can hear the relay tick sound.
Hi Gayan,
We havn't got to that stage yet.
Its just Pin #2[D0 out] and Pin #18 [Gnd] that needs to be debugged first.;)

Eric
 
hi catz,

I have checked my BIOS settings:
Parallel Port: Enabled
Mode: EPP
Base Addr: 378
IRQ7

SET your PC to EPP Mode.

The test program I have sent you works, a number of people have used it and its been in use a long time.

So,
Some other suggestions, you may have tried these already, but you never know.

Have you wired the 25way 'D' Connector youself?
Are you sure you have correctly read the plug pin numbers.
If in doubt, use a magnifying glass and read the embossed pin numbers near the solder buckets.

Have you linked ALL pins #18 thru #25 together as the Gnd 0Volt common.
I have seen some PC's that dont have all these pins connected internally.

The diagram you have posted shows the solder pin side of the 25way 'D' cable plug.

Are you able to temporarily install a parallel printer, for test, to check out the parallel port drivers?

With the test program running and the 'Read Input' box enabled, you should be able to connect in turn
to pin #18,,,, each of the pin# 11, 12, 13 and 15.

As you ground these pins the Test program should display the state of the input pins as you Ground each pin.

[set the Test program to 'Beep@Read'], the port is read once every second.

Let me know what you have tried and the results you get.

Eric
EDIT:
Just read your PM to me, named 'Succes' with following text.

it is working exactly the same way as u have told
...but it is giving just 4.5v


Do you mean its switching OK and the pin voltage only reads +4.5V and not the +5V you are expecting????
Please give more details
.
 
Last edited:
hi eric i have tried what all u have said using the program u have given me it is switching of and on ....when it is on it is giving 4.4 to 4.6v between pin 2 and 18 and i have connected all the pins from 18 to 25...the test program is displaying the state of each pin when they are grounded( the led is glowing and stoping)
 
nightcatz said:
hi eric i have tried what all u have said using the program u have given me it is switching of and on ....when it is on it is giving 4.4 to 4.6v between pin 2 and 18 and i have connected all the pins from 18 to 25...the test program is displaying the state of each pin when they are grounded( the led is glowing and stoping)

hi,
The pin output voltages on the port are never the full +5V.
Its normal to have about +4V to 4.7V, its not a problem.

Whats the next stage of the project are you going to add the other components shown in your circuit?

Eric
 
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