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Topic: How much harm can 100 mA make? |
Don R Brown
From:
Rochester, New York, USA
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Posted 14 Sep 2015 7:05 am |
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I note the AC adapters for Boss effects pedals have an output of 9V, 200 mA. I have a spare adapter kicking around, same output plug, same polarity, output is 9V, 300 mA.
100 mA does not sound like much but it's 50% over what comes with the device. Is it safe to use that spare gizmo, or am I risking damage? |
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Jack Stoner
From:
Kansas City, MO
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Posted 14 Sep 2015 7:19 am
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A higher current rating is not a problem. The unit will only draw what current it needs. You won't have any problems.
However you must make sure the voltage is what is required. Most require 9VDC, but there are a few that require 9VAC. |
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Loren Morehouse
From:
Meadowlands, MN USA
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Posted 14 Sep 2015 7:35 am
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| I get a kick out of these power supply's for different things. Anything from household to electronics. If they say it puts out 9VDC it's usually 12 or higher. |
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Don R Brown
From:
Rochester, New York, USA
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Posted 14 Sep 2015 9:06 am
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Thanks Jack & Loren!
I'll put a meter on it and be sure what I have. |
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Robert Parent
From:
Gillette, WY
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Posted 14 Sep 2015 10:39 am
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Most of those power supplies without a regulator will put out the marked voltage at the rated current. If your device draws less current then the voltage will be a bit higher than marked. Measuring the non-regulated style without any load will always yield a higher voltage.
Robert |
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Scott Duckworth
From:
Etowah, TN Western Foothills of the Smokies
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Posted 14 Sep 2015 4:16 pm
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And most devices that have unregulated power supplies (aka Wall Warts) have regulator circuits built into the device right after the power connection...
_________________
Amateur Radio Operator NA4IT (Extra)
http://www.qsl.net/na4it
I may, in fact, be nuts. However, I am screwed onto the right bolt... Jesus! |
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Keith Hilton
From:
248 Laurel Road Ozark, Missouri 65721
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Posted 14 Sep 2015 7:04 pm
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Jack is correct as usual. Few people know the difference between a regualted 9 volts DC power supply, and non-regulated 9 volt DC power supply. Another important thing is the polarity of the tip, is it positive or negative? Another important thing is the barrel and tip size. The most common sizes are 2.1X5.5mm and 2.5X5.5mm
You can burn up a expensive electronic device, if the device requires a 9 volt DC regulated power supply, and you plug in a 9 volt DC un-regulated power supply. |
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Don R Brown
From:
Rochester, New York, USA
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Posted 15 Sep 2015 5:30 am
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OK, so let me be sure I understand.
If I test the device just plugged in to the wall, but no load, if it is rated at 300mA and is regulated, that's what my meter will read. But if it's unregulated, it will read higher than 300 mA?
Polarity is not a problem, the supply which came with the device, AND the one I am considering using as a spare, both have the polarity marked on the label and are the same. |
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Georg Sørtun
From:
Mandal, Agder, Norway
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Posted 15 Sep 2015 5:58 am
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Available current, declared in mA, is just that: available current. That could be 2000 mA (same as 2 A) without making any difference as long as the connected unit does not draw more current than what is available - in your case 300 mA. With no load (just a meter) the current drawn is near zero, and you better not try to load the power supply with the meter for current since that is likely to blow fuses and/or destroy both the meter and the supply.
What matters is what Voltage that is delivered at a given load. For a regulated power supply the output Voltage will be pretty stable regardless of load - current drawn - up to max load, while an unregulated power supply (especially the tiny and cheap wallwarts) can deliver 50 to 100% higher Voltage unloaded compared to fully loaded. Measuring the Voltage unloaded will just tell you if the power adapter is unregulated or regulated, and not much else.
All effect pedals designed for 9 Volt DC will handle supply Voltages up to 12 Volt just fine, and most can handle higher Voltage than that - 15 Volt or so.
Thus, if (as you write) the polarity is correct, plugging the power adapter to the effect pedal should work fine. |
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Paul Arntson
From:
Washington, USA
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Jon Light
From:
Saugerties, NY
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Posted 15 Sep 2015 8:40 am
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Regarding rated amperage, forgive the stupid example but---
Buy a workbench that is rated to hold 300 pounds. Pile 100 pounds of junk on it...no problem. Get close to 300 lbs of junk...proceed cautiously. Exceed 300 lbs, danger.
Plug a stompbox that draws 150mA into your 300mA power supply and you can still daisy chain a few more effects. Just keep track of the cumulative mA draw of the boxes. Exceed the 300 mA rating of the power supply and it will burn out. |
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Don R Brown
From:
Rochester, New York, USA
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Posted 15 Sep 2015 9:06 am
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So I finally get time to look into this, and see if I'm getting 9v output - and my test meter is dead. I go to replace it, and I don't have a spare battery that size. And - it's a 9v battery! I feel like I'm going in circles!  |
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Stephen Gambrell
From:
Over there
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Posted 17 Sep 2015 7:11 am
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| Maybe, Solar? |
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ajm
From:
Los Angeles
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Posted 24 Sep 2015 7:59 am
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Don: Stop.
You didn't say what adapter you are using. You also didn't say what you are trying to use it with.
"If I test the device just plugged in to the wall, but no load, if it is rated at 300mA and is regulated, that's what my meter will read. But if it's unregulated, it will read higher than 300 mA?"
No offense meant, but it sounds like you do not understand basic electronics.
Are you measuring the current? It sounds like it.
You do not need to measure the current. In fact, if you set your meter to measure current, then place the probes across the output of the adapter, you will essentially short out the adapter. Bad. You may blow a fuse in the meter, or possibly "hurt" the adapter. Therefore, forget about measuring the current.
Your adapter should have a label stating what type it is.
AC or DC volts.
Current output maximum.
Input voltage (probably 110 or 120 VAC).
Let's assume that it says 9 VDC, 300 ma.
Let's assume that the plug is a standard BOSS 2.1 mm barrel type.
Plug the AC adapter into the wall.
Set your meter to measure DC volts.
Put the + probe on the outside of the plug.
Put the - probe on the inside of the plug.
At this point you are essentially drawing no current (zero ma) from the adapter.
The meter should read between +9 VDC and about +12 VDC.
If it reads close to 9 VDC it is most likely a regulated adapter.
If it reads around 12 VDC it is unregulated.
For most stomp boxes you won't hurt them if you use the adapter.
As you plug in one or more effects you will start drawing current from the adapter, and the voltage will drop.
If the voltage reads negative, STOP.
You either have the probes reversed, or you have an adapter that puts out -9VDC instead of the more common +9VDC.
As was said, make sure that whatever effects you use match the polarity of the adapter. If the effect(s) require +9 VDC, only use an adapter that is a positive output.
How big of an adapter do you need? How much current does it need to supply?
Look at the effects being used. They might say how much DC current they require/consume. If they don't, and they can also run off of a 9v battery, then as a rule they probably don't use more than 20 ma worst case. If you have five effects pedals, and they all run off of 9v batteries, then I'd figure that together they all would not draw more than 100 ma, and in reality they probably don't draw that much.
Hope this helps. |
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