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Author Topic: atmega168 pin connectionr(50$ robot)  (Read 1567 times)

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Offline javilaTopic starter

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atmega168 pin connectionr(50$ robot)
« on: June 02, 2010, 12:41:52 PM »
Hi: Me and 2 friends started building the 50$ robot separately, I got it to work and they could not. Now, when I was checking their board against mine I noticed that they had the AVcc pin connected to the VCC pin on the board which according to the pdf schematic is correct. I had not connected this pin and my board was working correctly(controlling servos, receiving input from sensors and led), my friend's boards were not being recognized by the programmer, so I told them to eliminate that connection and it worked for both of them.
 Why is that? The schematic says that you are suppose to connect those pins and when I tried just to see what would happened to mine, the controller got really hot as well as the regulator.
Is the schematic wrong? I have the atmega168. Like I said everything works fine without that connection.

Offline Choco_liger

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Re: atmega168 pin connectionr(50$ robot)
« Reply #1 on: June 03, 2010, 02:50:02 AM »
Is your VCC connected to AREF on the IC?

Offline Razor Concepts

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Re: atmega168 pin connectionr(50$ robot)
« Reply #2 on: June 03, 2010, 02:54:53 AM »
It sounds like you are connecting the wrong pins (instead of AREF to VCC, sounds like ground to VCC). The only reason the controller should get hot is if the ground and VCC are shorted together.

Offline javilaTopic starter

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Re: atmega168 pin connectionr(50$ robot)
« Reply #3 on: June 03, 2010, 08:14:38 PM »
Right now Avcc is connected to Aref but Vcc is not connected to anything(well only the led). Like I said... this way it is working fine(led works and the Vcc has a voltage) but it seems to be incorrect based on the schematic.
The other two boards had the Vcc connected to the Aref and Avcc but did not work with the programmer, once they disconnected the Vcc from the Aref and Avcc like I have mine, the programmer was able to read the signature and program.
But the schematic says that Vcc should be connected to Avcc and if I am not mistaken the datasheet says the same..
I do not get why it is working fine without that connection and not working with it.

hopefully I am making some sense

Offline Razor Concepts

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Re: atmega168 pin connectionr(50$ robot)
« Reply #4 on: June 03, 2010, 08:35:18 PM »
Are you using the color-dot schematic or the visual layout PDF one?

Offline javilaTopic starter

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Re: atmega168 pin connectionr(50$ robot)
« Reply #5 on: June 03, 2010, 08:39:47 PM »
pdf

Offline Razor Concepts

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Re: atmega168 pin connectionr(50$ robot)
« Reply #6 on: June 03, 2010, 08:53:50 PM »
Did you uncheck the "micro controller" box to hide the chip and reveal the connections inside?

Did you mirror the connections by accident? The PDF shown is a TOP view of the board, so when you go unto soldering the bottom, you will have to be careful and flip the connections properly.

Offline javilaTopic starter

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Re: atmega168 pin connectionr(50$ robot)
« Reply #7 on: June 03, 2010, 09:08:57 PM »
No no, i did missed the connection from Avcc to Vcc because it was under the microcontroller on the schematic.. But it works without it, mine only got hot when I connected it, so I disconnected it and it works fine.... And for my friends it did not work with it, only when I told them to disconnect it.
Why is it working fine without the connection Avcc to Vcc?

Offline Razor Concepts

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Re: atmega168 pin connectionr(50$ robot)
« Reply #8 on: June 03, 2010, 09:32:42 PM »
While they are not connected, measure the voltage from avcc to ground and vcc to ground. Both should measure 5 volts.

Offline javilaTopic starter

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Re: atmega168 pin connectionr(50$ robot)
« Reply #9 on: June 03, 2010, 09:41:13 PM »
I really appreciate your help Razor...
Yes they both have 5V while not connected to each other... But arent they supposed to actually be connected to each
other(according to pdf)????

 


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