Minimum Power Supply Voltage when Programming M2 Picaxe

H

hal8000

Member
In Picaxe Manual 1 page 25, M2 and X2 parts can work between 1.9 and 5.5V

However if the power supply was3.3V would programming a 20M2 Picaxe cause
damage as the AXE027 USB lead supplies 5 Volt?

I've already killed a 20M2, because I missed off the 22k/10k resistor network
to serialin. My faullt for working late one night.


Until I hear otherwise I will always use 5V when programming then remove
the AXE027 and power off before using 3.3V
 
hippy

hippy

Ex-Staff (retired)
With the 22K/10K download interface fitted; a PICAXE can be safely programmed from an AXE027 cable no matter what the PICAXE power supply voltage is.

The AXE027 includes 100R inline serial resistors on its input and output so, when programming a 3V3 PICAXE without a download interface, this should limit the injection current to 17mA which should not normally be enough to damage the PICAXE chip but may depend on other factors.

Fitting the download interface resistors would be the recommendation.
 
A

AllyCat

Senior Member
Hi,

Yes indeed. Recently my computer got "confused" and kept reporting programming errors and I was convinced that I had three "dead" PICaxes. Interestingly the Error Message suggested that the supply rail should be reduced from 5 volts to 4.5 or less. But with a reboot and a few Hard Resets, they're all working again. ;)

However, the two programming resistors are important and should never be omitted (as you may have learned the hard way).

Certainly PICaxes can be programmed at 3 volts and I've recently succeeded at below 2 volts! Personally, I've always used "real" or USB COM ports for my PC interfacing and recently found that programming only ceased when the Vdd was so low that the SerOut interface had stopped working. That was one of the reasons for devising and documenting this project.

Cheers, Alan.
 
H

hal8000

Member
Had tried a hard reset, also left it for 24 hours and my 20M2 had gone short circuit. Was drawing 200mA from a 5V supply
Ironicly had the two resistors on the veroboard and used a wire link to the serial pin. However it was late at night I'd misconnected
the wire link so the serial pin had full 5V without current limit, which is what caused the damage.

Luckily I always buy in multiple quantities so have spares..... the moral for me though is not to work
late at night.
Nice project BTW, AlleyCat have it bookmarked.
 
You must log in or register to reply here.
Top