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Topic: Help reading voltage on an analogread pin (Read 4173 times) previous topic - next topic

Anachrocomputer

The parts list is OK.

It's very risky to connect a 12V laptop to a car's electrical system.  The "12V" supply will vary from 10.5V to 14.8V according to whether the battery is fully discharged, charged up and floating, or on charge from the engine/alternator.  The voltage will drop when starting, possibly as low as 9V.  

You will need to find a specially-designed power regulator for automotive use, to avoid frying the laptop.

StealthRT

Anachrocomputer: Alrighty, check on the parts list! :)

How does this look for the regulated 12v?



David

Anachrocomputer

That regulator looks like a good 'un.  It has various protection circuits, and noise suppression.  The regulator chip is rated at 5Amps, so if that's enough for your laptop, go for it!

StealthRT

Well from what i gathered from the Car Adaptor for the EEE PC it is rated as:
Quote

input:  12-24VDC
output:  12 VDC 3.0A

And its said on a forum that if you go higher than 3.0a than you can hear the "whine" in the engine though the speakers.

Any replacement part for the 5a then? I think it would be better for me to buy a $15-20 car charger since the bnx002-01 alone is $10!

http://www.mwave.com/mwave/DeepSearch_v2.asp?scriteria=asus+charger&ALL=y&TP=

David

Anachrocomputer

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Any replacement part for the 5a then?


I don't understand what you mean here.  The regulator part in the diagram is rated at 5Amps, and according to your info, the EEE PC takes 3Amps, so we're OK.

You may, however, be better off buying a ready-made car charger, as you suggest.

StealthRT

True but like i said in my last post.. and rating higher than 3a makes a "whinning" o "buzzing" noise thoughout the lappy.

So i guess my best option would be to just buy the pre-built one and be done with it :)

David

StealthRT

Alrighty,... trying to connect this thing up to the relay... heres what im thinking...

This is what the relay looks like:


- 1 (COM) connected to one side of the power switch
- 3 (NO) connected to the other side of the power switch
- 2 Connects to 5v line
- 5 connects to the Arduino digital pin out (5v)

Will the 3 (NO) have 5v coming out of it? If so, i need it to have 0v since its just triggering the power switch.

Here is the PDF for the relay: http://pewa.panasonic.com/pcsd/product/pwr/pdf/mech_eng_js.pdf

Thanks!
David

Anachrocomputer

Quote
- 5 connects to the Arduino digital pin out (5v)


Pin 5 of the relay goes to the collector of the transistor, assuming you're following than plan.

Quote
Will the 3 (NO) have 5v coming out of it?


The contacts are completely isolated from the 5V and ground of the Arduino.  So the only thing coming out of pin 3 will be whatever went in on pin 1, when the coil is energised.  When the coil is not energised, there will be nothing connected to pin 3 by the relay.

StealthRT

Alright, well this is how i wired it up (and it seems to work fine)
Code: [Select]

- 1 (COM) connected to one side of the power switch
- 3 (NO) connected to the other side of the power switch
- 2 Connects to Ground
- 5 connects to the Arduino digital pin out (5v)

I also tried putting the resister and the TO-92 on the relay and it didn't seem to have enough volts coming from the chip (around 1v or less). So i don't know why it called for a 2k ohms resister into the TO-92. I had the resister going into the "B" and the "E" going to ground and the "C" going into number 5 on the relay.

Once i tool the resister and TO-92 out, it turned the relay on straight from the chip to number 5.

Here is the final schema the guy used (notice where he doesn't even use a relay to turn on the power switch:


Now i would like to hook the power up so i can turn the laptop's power on/off at will. Using the schema above, this is what i think i need?

Here's a drawing i made in order to hook up a pin to unlock a car door.


Here's the 12v relay i got for this job: http://www.components.omron.com/components/web/pdflib.nsf/0/7270ED3CFB55EBFF85257201007DD4FF/$file/G8QN_G8QW_0607.pdf
Its the G8QN-1C4 DC12

thanks,
David

StealthRT

#24
Feb 28, 2009, 02:21 am Last Edit: Feb 28, 2009, 02:42 am by StealthRT Reason: 1
I hooked it up like i have in the drawing but it doesnt seem to work..

When i ground it and supply the 12v to the 86/85 pins it opens up without it even having the 5v signal off of the chip? Once i add the 5v from the chip it still doesnt do anything... What did i connect wrong?

I used the following:
- NPN/25v/1.5a/120-200 small signal transistor
- 1k resistor
- 12v SPDT relay
- 1N4004 400v 1a standard rectifier

Thanks.

StealthRT

Ok, i drew what i currently have it hooked up like:


David

StealthRT

Any input on this, Anachrocomputer? Keeps staying open when i provide the 12v on the other side of the relay!

I'm simulating 5v coming from one of the digital pins. I'm getting about 0.76v from the base. I'm getting about 0.03v from the C when connected to the 12v as well.

David

mem

Double check that your wiring is actually the same as the diagram. If it is and you get 12 volts on one side of the relay coil and 0.03v on the other then the relay is probably faulty or specified for a higher voltage.

StealthRT

Yeah i still get 0.03v on one side and 12v+ on the other. The relay requires 12v to open and that's what its doing... but its not doing it correctly.... It needs the 5v pin to trigger the other side of the 12v and right now, its opening when i supply one one side with 12v...

David

StealthRT

Alright, correction... its 4.62v when i DO NOT supply the 5v to the output pin and 0.03v when i DO supply the 5v....

David

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