Px24 Hot?

john hauton

Hi,
I have a bs2px24 on one of milfords development boards, just running flashing leds on the output pins. The px24 is supplied by the 5v regulator on the dev board.

Should the processor chip on the px24 get quite hot?

Thanks & regards... John

Mike Green

It depends on what you mean by "quite hot". The BS2px is a fairly fast version of the Basic Stamp, so it would normally run warmer than say the BS2pe which is optimized for lower power consumption. If you're running a lot of LEDs with fairly high average current consumption, that could also cause the BS2px to run hot.

The SX processor used by the BS2px is designed to run normally in temperatures up to 85C which could feel very hot to a finger touch.

john hauton

Hello Mike, I would think 85 degrees would be about right. On this dev board there are two row of ten leds (bargraph) each fed through a 1k resistor. So I would guess somewhere about 5mA each pin. So long as the chip is meant to get hot thats ok.

Thanks for replying so quickly.

Regards John

Mike Green

It all depends on how many LEDs are on at a time. If all were on, that would be 20 x 5mA = 100mA. Although this is probably within the absolute limits of the SX chip, it's still pretty high (see page 52 here).

john hauton

Hi Mike

From what youve told me, and whats in the datasheet (thankyou) it seems I havent been kind to my px24.
On this dev board each io pin goes through a 1k resistor to one segment of a ten segment bargraph display. I wrote a test routine which toggles each output in turn, in an endless loop. The problem is it runs so fast that the leds appear to be all on apart from the toggling one.
As I dont want to do any damage, I think I will change the value of the limiting resistor.


Thanks for all you help


regards John

Mike Green

If you only have one LED on at a time using a 1K series resistor, that's only 5mA average current, not much at all and certainly way below the maximum.