Voltage problem on PICAXE-08

[m_pratley]

Hi,

I have a PICAXE-08 board which I have built with standard components apart from R2 where I have substituted the 22K resistor with a 33K resister as I damaged the 22K one (pulled a leg off).

The flowing is done on an empty board, program cable removed, jumper in PROG position. The chip is a brand new 08M, and pin 1 is aligned with arrow.

When I connect to a battery (new AA's) and measured the voltage, I get 4.52V, connect to board and I get 0.1V, unplugged and checked battery, still 4.52V. I try a 100uF capacitor and reconnect, 0.45V, and when disconnect 4.52V. The current is less than 1mA, and settled down about 72uA.

The resistance between + and - is Millions of ohms. I have checked the circuit and all looks fine.

Can anyone suggest anything?

 

[thelabwiz]

Do you have any "floating" (unused) pins? Are they tied to + or ground via a resistor of 1K to 10K?

What voltages are on the socket pins?

Looking down on the *top* of the chip:

<code><pre><font size=2 face='Courier'>
1 notch 8
2 7
3 6
4 5
</font></pre></code>

With this layout, 1 is + and 8 is -.

John

 

[hippy]

Sounds like a short on the board. Remove the PICAXE chip and measure the voltage again. If it's still near 0V then check for solder bridges or stray strands of wires.

 

[m_pratley]

Thank you for your replies.

I have remove the chip, still reading close to 0v. Am going to check the board for shorts, not many components so shouldn't take long.
I didn't understand about the floating pins reply, I have other proto board that work perfectly.
I do not understand what would cause the voltage to drop without the current increasing. It can't be the battery connections to the board as I measure the voltage on the battery terminals.

 

[eclectic]

m_pratley,

I THINK I might have an answer.
I've just removed the 08M from a protoboard.

Look at the BACK of the board.
There are three solder connections very
close together.
Res 1 / Res 2 / 08m v+.

I deliberately shorted Res 1 and V+.
And got a reading of about .45 volts.

Have you got a decent magnifying glass?
I certainly needed one!

e.