power drain/LED isue

[donis]

Hi, as you may know from the previous topic, i am building the 50$ robot. yet again the circuit looks fine and everything gets the power and stuff though LED isnt working/indicating anything. it does work if i hook it up with circuit gnd, but it causes fast power draint and it is supposed to be conected just to the resistor. so what could be wrong?

also my voltage rogulator does work, but it gives out ~6.5 v not 5 as it should, is this going to cause some trouble?

[Soeren]

Hi,

Hi, as you may know from the previous topic, i am building the 50$ robot. yet again the circuit looks fine and everything gets the power and stuff though LED isnt working/indicating anything. it does work if i hook it up with circuit gnd, but it causes fast power draint and it is supposed to be conected just to the resistor. so what could be wrong?

How large a resistor did you use?  (Don't just look at it, measure it with an Ohm-meter).
Never connect an LED without a resistor, it will die or get seriously impaired in a few ms.

also my voltage rogulator does work, but it gives out ~6.5 v not 5 as it should,

That's not really within the definition of a working 5V voltage regulator!
Anything above 5.25V and it's either connected wrong or damaged.

is this going to cause some trouble?

Yes!

[donis]

Hi,

Hi, as you may know from the previous topic, i am building the 50$ robot. yet again the circuit looks fine and everything gets the power and stuff though LED isnt working/indicating anything. it does work if i hook it up with circuit gnd, but it causes fast power draint and it is supposed to be conected just to the resistor. so what could be wrong?

How large a resistor did you use?  (Don't just look at it, measure it with an Ohm-meter).
Never connect an LED without a resistor, it will die or get seriously impaired in a few ms.

also my voltage rogulator does work, but it gives out ~6.5 v not 5 as it should,

That's not really within the definition of a working 5V voltage regulator!
Anything above 5.25V and it's either connected wrong or damaged.

is this going to cause some trouble?

Yes!

i used 330 ohm resistor, is it too large? (i just checked it and it actually doesnt go higher than 200 ohms though i have a really cheap multimetre and it could be lying)

it is possible that the voltage regulator is damaged cause i made some mistakes while soldering (at the begining), should i just replace the regulator or it would be better to remake whole circuit? also is there a way how to check if my microcontroller is ok because its been plugged in while receiving power.

[Soeren]

Hi,

i used 330 ohm resistor, is it too large? (i just checked it and it actually doesnt go higher than 200 ohms though i have a really cheap multimetre and it could be lying)

OK, perhaps you have misread a 220 Ohm for 330 Ohm, sometimes it's hard to differentiate red and orange on resistors.
Shouldn't make that much difference though.
Cheap DMM's are usually quite precise.

it is possible that the voltage regulator is damaged cause i made some mistakes while soldering (at the begining), should i just replace the regulator or it would be better to remake whole circuit? also is there a way how to check if my microcontroller is ok because its been plugged in while receiving power.

The regulator may well be dead.
The controller might work, but if it got 6.5V, it might be dead as well.

To test it, build the circuit and test voltages and connections before you break out the controller - which should be installed last (and in a socket).

Then you load a test program into it just flashing the LED for starters.

[donis]

thanks, i'll try to fix the circuit as soon as i get new parts.

though i bet ill have some questions/isues latter too.

[donis]

i just took out the voltage regulator from the circuit and tested it just - it gives out 4.95v so thats as it should be, though when in the 50$ robot circuit it was emited 6.5v

what else could be wrong with the circuit?

[waltr]

Recheck all of your parts and connections.
Are all diode polarities correct?
Are all electrolytic and tantalum caps polarities correct?
Look for solder bridges, shorts, with a magnifier and an Ohm meter.

Is the processor in a socket? If so remove it and re-test the regulator in circuit.

[donis]

Recheck all of your parts and connections.
Are all diode polarities correct?
Are all electrolytic and tantalum caps polarities correct?
Look for solder bridges, shorts, with a magnifier and an Ohm meter.

Is the processor in a socket? If so remove it and re-test the regulator in circuit.

polarities were correct and i didnt find any shorts though i could have messed up smtn. with soldering.

i already scrapped my circuit and decided to remake it so i cant check it anymore but yes the processor was in a socket.

anyhow thanks for advice.

now i need to check if my processor isnt damaged so i decided to make a LED blinking programm and test it as i was suggested, however, i cant quite figure out the circuit scheme i should be useing 'cause i'm still new at this, could someone explain what should go to which pin? i dont know how those ports a/b/c/d etc. works.

[knossos]

i just took out the voltage regulator from the circuit and tested it just - it gives out 4.95v so thats as it should be, though when in the 50$ robot circuit it was emited 6.5v

what else could be wrong with the circuit?

Fixed voltage regulators can also be used as adjustable regulators as well.  In your application as a fixed regulator, your GND pin should connect directly to ground. 

If it was connected between two resistors (a basic voltage divider) it would act like a voltage boost regulator outputing a higher voltage.

Google voltage regulator circuits and adjustable regulator circuits, or look at the application notes in this datasheet.

[donis]

Fixed voltage regulators can also be used as adjustable regulators as well.  In your application as a fixed regulator, your GND pin should connect directly to ground.  

If it was connected between two resistors (a basic voltage divider) it would act like a voltage boost regulator outputing a higher voltage.

Google voltage regulator circuits and adjustable regulator circuits, or look at the application notes in this datasheet.
[/quote]

oh, i guess that was smtn like this though i had only one resistor but i also had 2 capacitators, probably their boost gave smtn too.

[Soeren]

Hi,

oh, i guess that was smtn like this though i had only one resistor but i also had 2 capacitators, probably their boost gave smtn too.

No, the caps have entirely different purposes and one resistor doesn't explain it either. Just write it off as something you can't explain and be very careful how you connect it up when you redo it.