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Picaxe power supply question

Hey guys i have  a quick power related question.

I have been playing with picaxe chips for a while now and I have recently been thinking about different ways to power these chips.  I have been powering up my projects just using AA batteries and a have come to the point where I need my project to remain powered on for larger amounts of time (days). 

 

 This lead me to the thought of plugging in my project to a wall outlet in my house.  I have heard of people using computer power supplies and such?  Just wondering if there is some type of DC power adapter that would best suit me need.  Would this be dangerous at all due to the fact that i am playing with a higher voltage?  Just thought I had better ask the experts here before going ahead and doing anything that could turn out badly. 

 I should also note that i am in Australia and im pretty sure we have 240v, 10A power here.

 

Thanks!

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You could readily get 5V from such a supply and it will likely offer a number of amps vs only 1 or 2 supplied by wall warts. To be fair, there would be a bit of finagaling to get the PSU to power up if it is an ATX supply. Nothing a quick internet search wouldn't fix though.

I don`t know if anyone has mentioned it, but if you do get a DC adapter for general prototyping and mucking about with circuits make sure its an isolated type.

Most SMPS adapters have no isolation from the AC side and a short could develop putting massive amounts of current through your circuit or yourself. Adapters with a transformer arent connected to AC and are a lot safer because the current is physically limited by the transformer windings.

Hey, that's pretty interesting. I didn't realize it, but the old linear power supplies that were common in "wall warts" have been largely replaced by switched mode power supplies (SMPS). I wasn't aware of this, or of the higher failure rates of the SMPS circuits in these adapters. Thanks for pointing this out.

These adapters seem to fail more easily due to transient overloads, and cheap ones may suffer from early component failure. Do you think a simple in-line fuse be adequate protection for these types of failure?  Maybe I'll rewire any AC adapters I use to add a quick blow in-line fuse. 

Search for old, unusable phone chargers. They work great and most of the time they are in the right voltage (3.7v - 5.0v).

The elecricity in your wall outlet is AC, and your Picaxe need DC. Many electronics use a small AC adapter to for power, which transforms the AC to a lower voltage and rectifies and smooths the AC power into DC power.

You can buy one or find one from some old electronics. For the Picaxe, you want something that supplies 4.5-5VDC, and enough current to supply the Picaxe and all the other stuff (motors, servos, etc.) you want to use. Add up the total current you expect to use, and make sure your AC adapter supplies more than that.

Awesome thanks for the reply,

The only one thing I am a little confused about is just the current.  I found this adapter on ebay

http://cgi.ebay.com/BRAND-NEW-5V-1A-AC-DC-Power-adapter-Power-supply-Wall-/320682243181?pt=LH_DefaultDomain_0&hash=item4aaa26b46d

 

Just say i use an adapter that supplies too much current, will that effect the picaxe chip in any way?

 

Thanks again! :)

the amp ratings on power adapters are maximums they can provide.    amps are "pulled" (or drawn) by your project, not "pushed" by the power supply.   therefore the adapter you referenced is 5v, 1a, means it will provide 5v at any current required by your project UP TO 1a.   you need to know how much current your circuit requires.  like IG says, make a list of all your components and how much current they draw to see if all is less than 1a.

are you sure you need to buy one?   a lot of people have a box, or a closet, or drawer full of old power adapters from old, busted things like clock radios, cordless phones, etc.

Thanks for the reply!

I think i might go for a dig through my closet and go adapter hunting!

The current rating is how much the adapter can supply. How much current is actually used depends on how much current your project draws.

Think of it as your project PULLING the current, not like the adapter PUSHING the current.

 

Thanks again,

Well explained!  :)