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Author Topic: 50 bucks project electronics problem  (Read 652 times)

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Offline Mike11Topic starter

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50 bucks project electronics problem
« on: June 13, 2011, 11:58:50 AM »
Hi,

I am new to robotics and am having a problem with the last step in the tutorial. I've just finished the electronics part, downloaded software and am trying to program it. But it behaves really strange! Either I get a red or flashing orange (thought I reckon I checked my wiring a million times so far) or get green (yay!) if I plug the microcontroller really lightly but then get a popup which reads: check ISP cable or the reset pin pullout,...) Voltage is around 1.6 - is that OK or too low? Also, when I plug in a rechargeable 9V battery (around 6,5 V now) it flashes green and shows that popup. It I plug in a non-rechargeable, newer 9V, my voltage regulator starts heating up but voltage according to AVR studio is around 1 V and the diode is always red or orange (I change the battery only). Could you please help me with that? What's the reason for that weird behavior connected to batteries? Shall the regulator heat up? What's wrong with my ISP cable when diode flashes green? I am totally hopeless... thanks

Mike

Offline rbtying

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Re: 50 bucks project electronics problem
« Reply #1 on: June 13, 2011, 01:11:26 PM »
The voltage should be 5.00v (plus/minus 0.05v), so 1.6 is definitely too low.  Do you perhaps have your voltage regulator installed backwards?

Offline Mike11Topic starter

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Re: 50 bucks project electronics problem
« Reply #2 on: June 13, 2011, 01:57:14 PM »
Hey, thank you! I reinstalled the regulator as it was really incorrect. Or at least it was opposite to the position of the regulator in the pics in tutorial. On the other hand, it was plugged correctly according to the visual diagram by Webbot. I think these two contradict a bit. Anyway, it now shows 0.9V and continues to heat up... Sigh

Mike

Offline adanvasco

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Re: 50 bucks project electronics problem
« Reply #3 on: June 13, 2011, 03:23:52 PM »
Make sure you are reading the datasheet for your specific voltage regulator. Don't ever go by pictures!!! They are just a reference. You should check the pinout on any device and connect it as needed. In this case, make sure you are connecting the grounds together, the input pin on the 7805 or whatever regulator you are using to the positive pole on the battery and the output pin should give you your regulated voltage.

Again, always read your datasheet and connect accordingly.
Knowledge does not weigh.

Offline Mike11Topic starter

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Re: 50 bucks project electronics problem
« Reply #4 on: June 16, 2011, 01:18:21 PM »
Yes, thank you. That's what I did and in fact, when I check the voltage in the AVR studio it shows 5.1! I am not able to get that figure with my multimeter but after I found this from the programmer I think the voltage should be OK. My wiring is OK too, no power bridges or so. Still, when I plug in the microcontroller, the voltage falls to around 1V and I cant program it. What shall I do? I have already tried three ATmegas. Am I so dumb that I havent plugged them in correctly and sth just blowed inside?

thanks, MIke

Offline Mike11Topic starter

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Re: 50 bucks project electronics problem
« Reply #5 on: June 16, 2011, 01:28:01 PM »
In fact, I ran all those three microcontrollers with the voltage regulator plugged in the opposite way (before I realised that). So did I really burn sth inside and shall I buy my 4th microcontroller? Can I somehow check if they're allrigth?

Thank you,Mike

Offline Soeren

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Re: 50 bucks project electronics problem
« Reply #6 on: June 16, 2011, 02:05:51 PM »
Hi,

In fact, I ran all those three microcontrollers with the voltage regulator plugged in the opposite way (before I realised that). So did I really burn sth inside and shall I buy my 4th microcontroller? Can I somehow check if they're allrigth?
You can start the sensible way and measure the voltages without plugging in the controller - i.e. measure the pins of the IC socket that should have 0V and +5V, to see what the voltage is without it.
Don't proceed with the controller until you read a crisp 5V.

If you haven't got the correct voltage, try lifting (only) the output pin of the regulator and measure that pin unconnected (referenced to 0V). Do you get 5V that way?
If so, you have something loading the 5V line and you need to check the board and wiring with a magnifying glass and plenty of light.

If nothing springs to eye, check the components hanging on the supply line, eg. a bad decoupling capacitor could be the culprit. The voltage regulator might be dud as well, especially if you reversed it initially.

Take plenty of notes while doing it.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline Mike11Topic starter

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Re: 50 bucks project electronics problem
« Reply #7 on: June 18, 2011, 02:56:51 AM »
Thank you very much.

I started the sensible way now and it seems better. In fact, I am not able to measure the proper voltage with my multimeter but AVR shows 5.1V so I think it's correct now (both with and without the microcontroller). I even have no problems programming now, everything seems OK. On the other hand, after I have programmed it, it does nothing (though everything seemed alright).

Mike

 


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