SURF PI POWER SUPPLY PROBLEM

[daverave]

i just took my surf pi apart to do some checks and i noticed the machine dies if the supply voltage go's below 9 volts...is this normal or is there a problem ??? also are there any mods i can do to make the machine less noisy at higher gain and more stable...i measured my pulse delay at around 15 us...my damping resistor is only 1/4 watt so not sure if that could make machine more noisy when it gets hot...any advice on these problems would be welcome.

[Polymer]

i just took my surf pi apart to do some checks and i noticed the machine dies if the supply voltage go's below 9 volts...is this normal or is there a problem ??? also are there any mods i can do to make the machine less noisy at higher gain and more stable...i measured my pulse delay at around 15 us...my damping resistor is only 1/4 watt so not sure if that could make machine more noisy when it gets hot...any advice on these problems would be welcome.

I was wondering just like you about why my surf pi would "die" at around 9.6v when slowly adjusting my PSU downward from 12v,
to simulate what happens when the batteries drain.

Couldn't find any real answer to this on the forum, like so often.
Replies like "it needs 12v to work" just won't cut it for curious tinkerers, like many of us are.

Soooooo many secrets appear to be kept here. That is the impression I have or maybe this "feature" just
serves certain individuals business interests who "help" a lot whilst also derailing interesting threads.

To me it looks like some people have a vested interest in keeping real information under wraps,
intentionally posting bollocks or faulty schematics so as to offer help against a fee thru backchannels.

To me this somehow poisons the whole spirit of what I thought this forum is about.
I have sadly seen excellent forum posters leave this forum, maybe because of this and/or other antics.

Oops, I've digressed and ranted ... but it's how I feel about this right now.

Daverave, sorry, back to the point:

Wanting an answer I poked around the Surf PI with my Oscilloscope and found what "dies" first when lowering voltage.
It was absolutely not what I had suspected it might be (the sound part).

Plain and straight: It has to do with U4/C not being triggered anymore.
Look at R4 & R5 forming a voltage divider (with the transistor).
Vary the value of one of the resistors to change the voltage going to the 4093 with a pot and you will see.

I managed to get my SPI to work down to 6.4 volts.
Of course going so low from 12v will open another whole can of worms.

I finally adjusted mine to drop out at 8.8v as sort of a deep discharge protection for the
eight eneloop AA's I am using.

Hope this helps. Cheers.

[waltr]

I was wondering just like you about why my surf pi would "die" at around 9.6v when slowly adjusting my PSU downward from 12v,
to simulate what happens when the batteries drain.

Wanting an answer I poked around the Surf PI with my Oscilloscope and found what "dies" first when lowering voltage.
It was absolutely not what I had suspected it might be (the sound part).

Plain and straight: It has to do with U4/C not being triggered anymore.
Look at R4 & R5 forming a voltage divider (with the transistor).
Vary the value of one of the resistors to change the voltage going to the 4093 with a pot and you will see.

I managed to get my SPI to work down to 6.4 volts.
Of course going so low from 12v will open another whole can of worms.

I finally adjusted mine to drop out at 8.8v as sort of a deep discharge protection for the
eight eneloop AA's I am using.

Hope this helps. Cheers.

Good detective work and thanks for posting.

[Tibuck19]

Do you let your car run out of gas? why would you let your batteries run dry.