What power supply (amps) would run this plasma globe?

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Discussion Overview

The discussion revolves around the appropriate power supply specifications for a 3-inch plasma globe, specifically focusing on voltage and current requirements. Participants explore various adapter options and their compatibility with the globe's needs, addressing both theoretical and practical implications of using different power supplies.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Exploratory

Main Points Raised

  • Some participants assert that a 4.5V supply with a 50mA rating is likely insufficient for a plasma globe requiring 5V and 300mA.
  • Others suggest that a 12V adapter rated at 1A is too high for the globe, questioning the safety of using it.
  • One participant mentions that the globe came with a car adapter but lacks a standard power plug, raising concerns about the specifications of the original adapter.
  • There is a suggestion to measure the output voltage of the car adapter to determine its suitability.
  • Participants emphasize the importance of not exceeding the rated input voltage and ensuring that the power supply can maintain 5V while supplying the necessary current.
  • Some express skepticism about the existence of a 5V 50mA power adapter, suggesting that common alternatives are typically rated higher.
  • USB power supplies are mentioned as potential sources, with some participants recalling that they typically provide 5V and at least 300mA.
  • One participant elaborates on the USB specification regarding current draw, noting that it can be complex and varies based on enumeration.

Areas of Agreement / Disagreement

Participants generally agree on the need for a 5V supply capable of delivering at least 300mA, but there is no consensus on the suitability of specific adapters mentioned. Multiple competing views remain regarding the implications of using adapters with different voltage and current ratings.

Contextual Notes

Participants express uncertainty about the actual output of the car adapter and the specifications of the original power supply. There are also unresolved questions about the implications of using adapters with lower voltage or current ratings.

Who May Find This Useful

This discussion may be useful for individuals seeking to understand power supply requirements for electronic devices, particularly those interested in plasma globes or similar low-voltage applications.

Abir
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my 3inch plasma globe needs 5V 300mA dc supply...
Can I use an adapter with 4.5V and 50mA output rating?
If can't then what will happen if I still do use it?
 
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Abir said:
my 3inch plasma globe needs 5V 300mA dc supply...
Can I use an adapter with 4.5V and 50mA output rating?
If can't then what will happen if I still do use it?

Welcome to the PF.

It most likely will not work. A 4.5V supply with a current rating of >=300mA might work, but an output current rating of only 50mA looks to be way too low.
 
I have another adapter with 1A rating but its 12V...i suppose that will be too high??
 
Abir said:
I have another adapter with 1A rating but its 12V...i suppose that will be too high??

Yeah, probably too high. Did the globe not come with a power adapter?
 
berkeman said:
Yeah, probably too high. Did the globe not come with a power adapter?
actually it did... but with car adapter not with a usb or power plug adapter..
I got it from ebay for 835 INR and the sales package details said nothing about it containg any adapter let alone specifying the type of adapter
 
Abir said:
actually it did... but with car adapter not with a usb or power plug adapter..
I got it from ebay for 835 INR and the sales package details said nothing about it containg any adapter let alone specifying the type of adapter

When you plug it into your car, does the globe work?

Also, can you measure the output voltage from the car adapter? If it's 12V (no down-regulation), then your 12V power adapter should be okay.
 
1. You should not go above the rated input voltage. If that's 5V, (does it say that on the globe?) then absolutely do not go above it.

2. You must be able to supply the 5V and the current specified. That is, when the globe draws 300ma, then the power source should still be 5V.
An adapter with 50ma rating will likely not put out 5V with a globe attempting to use 300ma

3. I find it hard to believe that a 5V 50ma power adapter even exists. Is it possible you are misreading it? 5V 500ma and 5V 1A are both very common.
(I take it back --- I guess they exist)

Just about any cellphone charger is 5V 450ma at least.
 
You need 5V. You need at least 300mA. (You might be able to get by a little low on that if the design engineer over built the supply.) But more current will work.

I seem to recall USB is 5V. I forget the current, but I think it will source 300 mA. So any USB supply should work.
 
The USB specification is that if you do not enumerate at all you not supposed to draw more than 2.5ma. for any length of time.
If you enumarate you and draw 100ma. You must not draw more than 100ma unless you enumerate and request higher power. Then you can draw 500ma.

The specification is actually much more complicated than that, including a sub-threshold signalling protocol, but I won't go into that.

Not all USB devices enforce this.
 
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