Measuring Effects Current Draw .. I

[Phend]

Current, in Milly Amps, is sometimes mentioned in the forum.
Measuring current can be with a DMM.
I have never done it though.
Discussion:
In an effect, where and how is it measured?
Measured for what reason? ie total current draw, how?
Is there an "idle" current and one when the effect is "being used"?
Power is 9 volts going into a DC jack.
What happens if to many effects are connected to a PSU?
Assuming they are all turned on at once, Rare occurrence.

thanks
 

[Lino22]

In an effect, where and how is it measured?
on battery or DC jack

Measured for what reason? ie total current draw, how?
to see how long will the battery last or what current draw capability power source to use

Is there an "idle" current and one when the effect is "being used"?
yes. but usually the active pedal power draw is higher just by the LED draw ... but alas, the LED draw can be 40x higher than the idle current, depends on LED and the current through it.

What happens if to many effects are connected to a PSU?
it will give lower and lower voltage than what it is supposed to

Assuming they are all turned on at once, Rare occurrence.
it really doesn't matter

[R.G.]

Lino's mostly right, only you can't measure the current in a DC jack powered effect by measuring at the battery connector. The current isn't flowing through there if you're feeding the pedal with a DC jack. But you can do that if your pedal has both DC jack and battery connector and you run it on battery alone to get a representative number. It'll pull much the same current on a fresh battery as it does on the DC jack; not the same, but very close.
Most simple effects and nearly all modern effects pull about the same current when bypassed as when engaged, excepting the LED current, as Lino notes. Some few, mostly older pedals turned the power supply current off entirely when bypassed, but this is quite rare. The LED current is often one to ten milliamperes, and this may be most of the "on" current. Some pedals pull much more active current in the circuit, though. You're right to measure.
What happens when too many pedals are connected to a PSU depends on the PSU, not the pedals. Some PSUs' voltage sags slowly and get much noisier; some sag abruptly at a cutoff/protection point; some cut off then "hiccup" on and off as they try to restart. Most modern switching power supplies do the last.
Interesting story (to me at least 8-) ) - a pedal and power supply company I know of has a policy of 100% testing each new batch of a new design of pedals. Their power supplies put out a lot of maximum power, about 1700 milliamperes. One test batch was acting funny, and they noticed that they had daisy-chained over a hundred of their pedals on ... one... power supply. The supply just kept on supplying.

[Phend]

Good stuff,
The DC jacks I have have a plastic housing, and a nut from the inside. 
I am using connectors that can be disconnected so I can take the pedal apart in one chunk sans plastic DC jack.
So I can measure mA there.
My latest project will have 9 effects on a purchased board.
Because 9 will fit, so why not.
Fuzz Face, Rangemaster, Chorus, Compressor, Foxx, Harm Perk, Tremolo, tbd, tbd.
None are digital, all are ones I have made in non metalic housings, each being battery powered.
Purchased a 1Spot w/ 1700mA Max output.
Problems here ?

[Lino22]

You would get away with a 100mA power source here.

Non-metalic housing? You know they should ne shielded. right?

[Phend]

These 9 effects will be in Hammond 1590 boxes.
So they are alumininum.
A winter project.

[R.G.]

Purchased a 1Spot w/ 1700mA Max output.
Problems here ?

No problem there. The 1Spot will probably power 50 or more pedals like you're talking about.

You don't say whether the Fuzz Face and/or Rangemaster are positive ground/PNP pedals. There are other issues that can arise from using a reversed ground/positive ground pedal in the setup. They're solve-able problems, but just be aware they're there.

[antonis]

Measured for what reason?

To know the value of power supply LPF series resistor in conjunction with affordable voltage drop, perhaps..?? 

[Phend]

Thanks R.G., No pnp, all, including the FF and RM, will be npn, neg gnd.

[PRR]

Rather than a current-meter, I would consider a voltmeter and a resistor. I have smoked too many meters by running the current THROUGH them. A common slip will cause "infinite" current which is bad.

With modern auto-ranging sensitive voltmeters you can read below 10mA on a 1-Ohm resistor, reads as 10mV (watch the "m" icon). Or 300mA with a 1r 1/10W resistor. You can have a 0.1r resistor for pig petals, or a 10r to get high resolution on nanopower petals (but why? usually just to know it is "low" is good enough). And if you get shorted to 9V or 18V the voltmeter is unlikely to be damaged (resistors are cheap).

On _AC_ an alternative is little doughnuts. I have that on my house power. If current went to 150Amps(here? Ha!) the little doughnuts run out of flux and their output is limited to like 15V, and no smoke. But doing that on DC is a little tricky and uncommon.

[Rob Strand]

Some traps for young players:

When you measure current you normally have to plug the meter leads into another set of terminals (200mA or 10A).

When you are finished measuring make sure you pull the leads out of the current terminals and put them back into the DMM's voltage/resistance terminals ASAP.

A very common problem is people leave the leads in the current terminals then later measure a voltage. That often blows the fuse inside the DMM.  It can also fry something in the circuit you are measuring because the DMM current terminals are close to short circuit.

[Lino22]

I have done that 3 times at least.

[GibsonGM]

...and in fact, if you go to measure something and the meter is doing very strange things even tho you're following the instructions to a T...you may well have a blown fuse. (or be plugged into the wrong jacks) 

Mine will show mV when testing a car's charging system, or full Amperes when measuring something that should be 20mA, sometimes making small beeps as if over range when clearly it's not.  I don't pop 'em often, but when it happens it sucks, so I keep a few of the right ones in the parts drawer.

[antonis]

Just place a slow-blow fuse in case of all effects CE amps work in phase..

[Phend]

From all, Great advice
I will abstain from trying to measure the current the toaster is using.
As far as 9v effects, sounds safe, check the plugs.
But I always wondered what would happen with a butter knife and toaster test.

[PRR]

...But I always wondered what would happen with a butter knife and toaster test.

I have numbers for my house. From street transformer to fusebox, 0.4 Ohms (this is high b/c cheap installation). Fusebox to toaster, say 50' #12 each way, 0.16 ohms. Add some hundredths for breaker and screws and splices, say 0.6 ohms. 120V applied to 0.6 Ohms is 200 Amps. As much as a truck starter, but at 10X the voltage so potentially 10X the molten metal.

This is 10 times the current rating of my 20A breakers. A standard time-curve suggests it will hold for about zero to 5 seconds and then trip (it is in the grey zone). It is also twice the rating of my 100A main breaker, it will hold for 90 seconds (except the 20A should blow much faster, it's not a Federal breaker).
https://global.discourse-cdn.com/internachi/original/3X/4/9/49af0b5c07416d6d3b6f4bcbdca82a411bd7e53c.jpeg

200 Amps in your face can burn you with hot metal or blind you with arc but it may be safer than a dull chainsaw. It may not vaporize the butter knife, that happens better with direct connected batteries or trash-can caps.

[FiveseveN]

I always wondered what would happen with a butter knife and toaster test.

For all your Joule heating needs check out Photonicinduction on YouTube:

Or more recently styropyro:

PS: Holy hell, Paul changed his profile pic!