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Topic: analog input alters voltage... doesn't read properly (Read 5 times) previous topic - next topic

DVDdoug

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I had it plugged in for like 20 seconds and then when i touched it on removal it was really hot...
How about those missing resistors to the LED display?

pcguru000


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I had it plugged in for like 20 seconds and then when i touched it on removal it was really hot...
How about those missing resistors to the LED display?


I don't understand why these would be necessary (is it just a best practice?)- its common anode so its just one 3.3v power source and then grounded lines - when not grounded they throw 3.3 volts. Seemed straight forward enough- and in practice, is working perfectly.

Regardless of whether the 7 segment display is connected (and i mean ANY of it) the voltage readings I get when the arduino is plugged into the GPS are the same... so this has nothing to do with it.


Runaway Pancake


Ah Thank you for this- I did not see Dougs post above and probably would have missed it all together if you didn't mention it.

I am power via the barrel jack HOWEVER I have a 5v regulator inline PRIOR to it- because I thought I'd aim for safer lower voltages (vs the 14.5 the bike throws).

As he said though- this is too little and could be causing strange behavior- I am going to wire in a 9V regulator that I have and see if that fixes it... hopefully that won't run too hot (really don't like it getting hot, at 14.5 volts the 328 chip actually scorched my finger a bit which was surprising.)

I'll post back here once I've tried this again w/ a 9v regulator.


Well, you could just put the output of the "regulated 5V" to the Arduino power header, but I wouldn't want you to biff it.
The 9V via the barrel jack is fine - I guess we'll wait.

Try not and go over 12V input.  Even so, the 328 wouldn't get "scorched my finger" hot unless there was something terribly wrong-o.

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I don't understand why these would be necessary (is it just a best practice?)"

And, yes, resistors with the LEDs are necessary, because LEDs aren't light bulbs. 
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pcguru000

Radioshack didn't have a 9v regulator in stock (I thought I had one, turned out it was a 12v :/) so I am gonna place and order and wait a few days...

As for the resistors and LEDS- reading about it- I am still not sure how this applies/works with a common anode 7 segment display- should i place a resistor in the 3.3v line?

In testing everything works 100% so I am not exactly sure why I need to add more components... (really was aiming for super simple lol, i am a web developer, not an electrical engineer afterall lol)

The arduinos 3.3v is the exact voltage the 7 segment requires to power it so I figured my input voltage is already clean, i don't need to adjust it. I understand that voltage changes can greatly affect the current draw from the led- but again, there isn't any change, just 3.3v...

Grumpy_Mike

Look if you don't understand what you are doing why the *** are you arguing. You need a resistor in seriese with each LED segment otherwise you damage things because your not in control of the current. Any one who thinks you don't need some sort of current control with an LED is just an idiot.

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