Poly-face power 18V?

[Itchy Scratcherson]

Greetings! short version: 18V or 9V supply?
more: The build docs for this cool phaser/envelope phaser have a contradiction. I followed the schematic (p.7) which shows you supply it with a 9V power source –so I'm currently verifying things using my Cioks DC7 set to 9V. However, at the end of the notes on p.8 of the build doc, in the Bias** paragraph, it specifically states "Remember for the right functioning of this circuit you have to plug it into a 18v power supply, make sure that all your electrolytic capacitors are suitable for 25v or more just in case." Am I missing some update or am I allowed to chide the doc writers? 

fwiw, the circuit uses an LT1054 (got mine from AES) along with LM7815 regulator... I've tried L78L15 and LM7815.
I assumed, ahem, the LM7815 would output 15V from a 9V source (from the schematic).

The board has 2 test points: one labelled "6.7V" & the other "15V". In non-envelope/ "Sweep" mode, I get very close to the 6.7V, but my power section, and it's "15V" test point currently shows just over 12V at best.

Build doc: https://pcbguitarmania.com/wp-content/uploads/2020/12/Polyface-Building-docs.pdf

Thanks for your help! ~Christopher

[Itchy Scratcherson]

Sounds great in any case... but madbean's Polytrog doc specifically points out that the LT1054 charge-pump is there so that it can utilize a 9V source & up it to 15V... or something to that effect.
https://www.madbeanpedals.com/projects/_folders/FilterMod/pdf/Polytrog.pdf

[idy]

Your PCBguitar mania board is like MBP board: It uses IC1,  a 1054 charge pump, to turn 9v into more (18?) then regulates it down to 15v with the 7815 regulator.

May big box EHX effects use the same power supply, a 24v unit, then put regulators inside to get what they need. People have added a charge pump to allow you to use a 9v wall wart.

The charge pump became a panacea for diy pedal builders but has a dark side; nigh pitch noise, sometime the ultra sonic switching interacts with other things to produce audibles.

[Itchy Scratcherson]

Thanks, idy! After replacing my LT1054 I see 14V, then tried a 3rd chip & now I get the requisite 15Volts. voila! 

[Itchy Scratcherson]

Follow-up question: at what point do you get concerned when the charge pump (or any IC) gets hot? In the past, if it can burn me I know something's wrong of course... So, how hot is acceptable?

[antonis]

For LT1054, ambient temperature of 25^oC and 1W power dissipation, case temperature of 40^oC should be marginally OK..
(considering junction temperature of 150^oC and R_θJA 85^oC/W..)

https://www.analog.com/media/en/training-seminars/tutorials/mt-093.pdf

P.S.
In case you want a plain answer: Mildly warm..

[Itchy Scratcherson]

Thanks! I realized my digital multimeter came with a temperature sensing attachment, and that I could look up the spec for any given chip. What a world we live in! 

[idy]

The other way to approach this, less prone to interpretation, would be to measure current. This is a series measurement which means maybe bending a pin out to the socket or other wise breaking the circuit and using your meter (set to DC amps!) to close the circuit.
LT1054 are rated for 100ma. I am not sure where you would measure the current output of the chip... Hoping one of the wiser ones will pipe up.

[duck_arse]

don't measure current out of the chip, measure it into the chip. the voltage across R2 will give you the current drawn, that and Ohm's Law.

[antonis]

the voltage across R2 will give you the current drawn, that and Ohm's Law.

R2 in exactly what schematic..??

[PRR]

R2 in exactly what schematic..??

Guessing game??

Mebbe in the PDF in the first post? R2 is a filter between +15V and the big CMOS chip.

[antonis]

So, are we talking about the voltage across that R2..??



I thought idy refered on charge pump (LT1054) and not on CMOS (4013) current..

[duck_arse]

argh. I really do need new specs. yes, guessing game. no, sorry, not R2, the resistor value is 2R2, rather oddly, and it is resistor R1. on the schem for the polyhog thing.

[PRR]

I really do need new specs.

No. We need no pastel-color JPEGified schematics! WTF?? Blue and white was good enough for most of history.

[bean]

You can successfully use the LT1054 although the circuit pushes it right up to the limit in terms of current draw. But, absolutely no issues with that. My "Polytrog" version of the Polyphase was probably the most tested/vetted build I've done for mbp. Of course, an 18v supply is always preferable over 9v with charge pump. But, not always practical for everyone.

[Rob Strand]

For LT1054, ambient temperature of 25^oC and 1W power dissipation, case temperature of 40^oC should be marginally OK..
(considering junction temperature of 150^oC and R_θJA 85^oC/W..)

https://www.analog.com/media/en/training-seminars/tutorials/mt-093.pdf

P.S.
In case you want a plain answer: Mildly warm..

If you use larger caps for C1, C2, say 47uF,  it might help.   I know when one cap is large an one cap is small the peak currents are somewhat higher than if both caps are large.   I'd have to look at the details.

[bean]

So, are we talking about the voltage across that R2..??



I thought idy refered on charge pump (LT1054) and not on CMOS (4013) current..

Looking at this, C1 isn't needed for charge pump only and can be omitted. A low ESR cap for C2 can improve efficiency.

[antonis]

Dunno about PS supply efficiency difference (if any) between Polyphase and Polytrog but the later saves few items..

[duck_arse]

I really do need new specs.

Mo.

Mo? what's Mo?

[PRR]

Mo? what's Mo?

Molybdenum. Element 42. Widely used to harden steel. Added to lubricants. Catalysts, even biological. De-Sulfurization of petroleum.

Or a typo.......