08M Problem

GGnz

New Member
Hi There,

Just programmed my first chip. It is a simple 3 LED chaser. However when it is hooked up to a 5V supply, the two LED's appear on and very dim on pins Out 1 and Out 2 while the other flashes. The flashing one is on Output 0. Also I don't have any resistance on the LED which must mean theres an output of 1.5V approx? I have it currently powered off 3x1.5V AA batteries (4.5V)

Any suggestions?

Also whats it mean the manual when it refers to leaving the Serial Out floating? I have this pin going to nothing on my main circuit board.

Regards,
Gareth
 
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Michael 2727

Senior Member
A floating pin is one that is not connected to anything ( floating in space )
The serin pin must be tied low if not connected to the D/L circiut.
( a 10K resistor to -NEG, 0V is the Rev-Ed standard used here )
If not, it may think it is high and wait for a new program to be downoladed.
A pullup resistor = ? Ohm value and tied to the +POS, 5V supply rail.
A pulldown resistor = ? Ohm value and tied to the -NEG, 0V supply rail.
The value in many cases can be 1K Ohms to 100K Ohms for the above
resistor values, Rev-ED use 10K for best all round function and protection issues.

In case this does not fix your problem, I suggest you also post the code you
are using as we are not mind readers and don't have a clue what you have done.
Although I hear Dippy has a cloudy Crystal Ball somewhere.
Welcome to the forum BTW.

PS: Read the Script again, "Serout" can be left floating
most Outputs can, but "Serin" input can't.
Most inputs work best if not left floating.
Most outputs don't really care, some RF outputs do though.
 
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GGnz

New Member
main:
high 0
pause 350
low 0
high 1
pause 350
low 1
high 2
pause 350
low 2
goto main


---

thats my code. im am missing the 10k resistor on my other circuit so putting one in now
 

Michael 2727

Senior Member
Nothing wrong with that code.
Check for short circuits if you've made your own board
or crossed wires if using BreadBoard.
 

jodicalhon

New Member
Also I don't have any resistance on the LED which must mean theres an output of 1.5V approx? I have it currently powered off 3x1.5V AA batteries (4.5V)
You must have a resistor in series with each LED. 330 ohms is a good value, but even 1k will be fine for now if that's what you have.
 

Michael 2727

Senior Member
Yes !, You MUST use a resistor, I missed that bit, prolly
the most important part.
Whatever the application, you can ONLY draw 20mA from any
single output.
Draw includes, SINK (use as Earth = Low Pin) or
SOURCE (draw Power from = Hi Pin )

PS: Dippy is/was on Hols, I noticed his tag here earlier.
Jeremy may also have one ?
 
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GGnz

New Member
I have 220ohm resistors hooked up to Super Bright 10000mcd LED's. Works fine with a straight 5V across them. Whats wierd though is the fact I can hook one of these LED's up to an output pin with no resistor and it flashes like it should. So the output is alot less then 5V. Have tried it on a few different boards now including my mates breadboard which is perfectly setup :S
 

jodicalhon

New Member
The output on the pin is a lot less than 5V because it is being clamped by the LED.

The rest of the voltage (5V - voltage across LED) is being dropped across the internal resistance of the output pin.

This is not good for your Picaxe.
 

BeanieBots

Moderator
Just because currents are low, it does not mean damage can't be done!
Putting an LED directly across an output overloads that output.
If it didn't, the LED would vapourise.
The fact that the voltage seen on the output drops is the same as the fact that when a spanner is dropped across a car battery, the terminal voltage of the battery is seen to drop. (just prior to the spanner melting and boiling acid being sprayed everywhere).

Why do people keep doing this? Is it because all the documentation says don't so the temptation to see what happens is just too great:confused:
 

GGnz

New Member
The PICAXE appears to still be working fine luckily. This is probably the reason the PICAXE got quite hot then. You see I would of thought the LED would of blown as opposed to working like it should. I might have to buy a finer soldering iron for this stuff I think.

Is there any tips for using a regulator? I have a 5V regulator hooked up to a Smoothing Capacitor, but wondering if this is all I need. This should be my last question for a while lol.
 

moxhamj

New Member
Yes, a 5V regulator, smoothing capacitor (anything from 33uF to 470uF) and for good measure, a 0.1uF cap across the picaxe power supply pins.
 
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