Question For Zachary Vex

[James P]

Zach

I know from personal experience your pedals last for ages on batteries. Is there any secret to low current draw i.e. choosing specific components, signal path design etc. Are there any particular components that draw a lot a power?

thanks

James P

[R.G.]

Zach's busy, he may not have time.

No, there is no set of inner secrets. Or I guess there is one: work really hard at knowing how the circuits work, figuring out the current used by each part, and then reducing it through detailed design of that part.

There are a few power hogs that you know after once: LEDs, relays, anything that gets hot. Other than that, you look at the specs and datasheets and figure out how to do it with less current. Pretty simple stuff really. No secrets.

To grow a smooth, green, perfect billiard-table like lawn like the ones at English castles: prepare the ground, till it, smooth it, fertilize and seed it, and when the grass comes up roll it with a lawn roller for two hundred years.

[Speeddemon]

I think most can be done with a low current LED (not in the signal path, but the indication light) that only consumes 1-2mA, and a low current op-amp, if you use opamps.

[Ge_Whiz]

Look at some of the low-current tricks Tim Escobedo uses too, at 'Circuit Snippets'.

[DiyFreaque]

Here's a suggestion for anything that uses a 555 - sub in a 7555.  The 555 is a pig when it comes to power; the 7555 uses a fraction of the current and performs the same function - it's a pin-for-pin replacement.  

Side benefit:  the 7555 is easier on the rails, so potential problems along those lines (clicking, etc.) rarely show up.

Cheers,
Scott

[James P]

Look at some of the low-current tricks Tim Escobedo uses too, at 'Circuit Snippets'.

Cheers Ge, i'd forgotten about Tim's site! Quite like the look of the TMK, or Tytewadd.

Thanks Guys

James P

[smashinator]

Here's a suggestion for anything that uses a 555 - sub in a 7555.  The 555 is a pig when it comes to power; the 7555 uses a fraction of the current and performs the same function - it's a pin-for-pin replacement.  

Side benefit:  the 7555 is easier on the rails, so potential problems along those lines (clicking, etc.) rarely show up.

Thanks for the great tip!

[WGTP]

Seems like someone said the 5532/5534 op amps a lot of folks like uses more current than most.  

The 4049 cmos chip has a bad reputation.

I noticed I left my Vulcan plugged in overnight and it didn't seem to matter.  

[zachary vex]

if you're having trouble predicting how much power your circuit will draw, test it in stages as you're building it by putting a mA meter on it (in line with the battery).

[Dai H.]

I remember reading something about higher total circuit impedance = lower current draw, then the opposite--which seemed to make sense to me.

[Processaurus]

Anyone tried using opamps and other ICs that have a shutdown mode for power hungry effects? Shutdown mode is a feature that makes the opamps outputs go to a high impedance state that saves power, but it can get out of the shutdown mode quickly.  You could set the shutdown pin in bypass with one of the throws on your 3pdt stompswitch.

I think the zvex lofi loop junky saves power in bypass mode by putting the recorder chip in a shutdown mode.  So does the white Boss tuner pedal, it draws 6 times as much current when its on than when in bypass.

[zachary vex]

yeah, the lo-fi does that, and some people notice the "thunk" on power-up as you turn it on (it's more obvious on some rigs).  one of the problems of using a sleep mode is that often you get a dc power-up noise which can most easily be avoided by putting in a mute or fade-in, which can be even more annoying!  i tried a fade-in for the lo-fi, but in the end there was 1] no room, and 2] it really annoyed me that the beginning of the loop didn't just come in at full volume.