K20d Off switch.

Is it?

I had always assumed that the on/off switch was just that: that it disconnected the battery from the camera.

That was until this evening when I had reason to look at the card. As I pushed it back in, the disc access light lit up. I kicked myself for pulling the card out with the switch on, but when I looked, it was off.

This leaves three possibilities-

There is another power source within the camera which lit the light.

There is a second power switch which is activated when the card is pushed in and subsequently turns off after a period of time.

The "Off" switch is actually a "standby" switch and there is still something running in the camera when it is switched off.

If the last one is the case (and I would guess it is) then people's assumption that batteries loose their charge over time may be slightly off the mark.

The "Off" switch is intelligent, and if the camera is doing something (like saving an image) it will remain "On" until the task is completed.

G

Indeed so George, but the camera had not been used since yesterday (:blush, so it would have been fully in whatever state "off" is.

After thirty years in electronics I can generally tell the feel of a proper voltage isolating switch, but this one might have beaten me.

When inserting the card the camera flashes twice to indicate that the card is recognised.

To my eye John, the light is flickering quite fast rather than on, so I would suspect it is actually reading something on the card.

The question is where is it getting the power to put the light on from.

I'm open to correction on this, but I did maybe read somewhere that when switched off the camera does still use a very very small amount of current.

If so, I would guess this is to speed up the ready time when it is switched on, a sort of standby situation.

Do all cameras not have a permanent power supply in order to maintain the internal memory for date, time etc.

That would make sense John.

These days small processing chips are fairly capable and use a tiny amount of current, and the camera has one as a 'watchdog' on all the time ready to fire up the main processor(s) when the camera is switched on.

Guessing, I would say not Barry. Modern memory does not necessarily need to be powered to remember what it is remembering (). If it did I would hope the battery for it would be accessible and I haven't seen it on my camera.

OTOH, if all the memory in the camera were non volatile, the 'take the battery out out for ten minutes' trick when the camera gets itself in a twist would not work.

I could understand no power if it were a fixed memory like the number of the last actuation. But the time and date need to run a clock, does that not require power? Typo

There are several ways that power could be applied to back up systems, but without asking Pentax you'll never know.

My guess is switching off still leaves the camera in reduced state of "power down" there will be an extremely small amount of power used to maintain the clock functions, possibly even a capacitor of sorts present.

My istD is still running on the button cell that was supplied with the camera and that must be what 5-6 years old? Maybe its decsendents have a small rechargable cell built into the body?

Good point Barry. Something has to be still running when it's off. That's why pcs have to have a battery and cannot rely purely on non volatile memory. I wonder how long it would take the camera to forget the date with the main battery out.

The suggestion is that there a second battery which we do not have access to.

There must be a second battery, or capacitor, otherwise the clock couldn't run when the main battery is removed.

I suspect that the camera draws so little power when "off" that the internal battery will last for ten years or so. And I suspect it's rechargeable, so there is no need ever to replace it.

G

I had noticed this light blinking for a while now and was curious but never gave any thought to it, until now I mean . And this was an easy one to test. I pulled out all the batteries, the grip and the body one and inserted the card and the light didn't blink this time. So conclusion is one of the above two statement. Definitely the light blinking the juice comes from the battery.

Good point Amin.