Using a mobile wall charger with PICAXE

Hi
I've read some posts about my question but I'm not sure about the appropiate answer.

Can I use directly a generic mobile wall charger (5V - 1000mA) to supply a chi035a board?
Any arguments for and against?

Thanks

I use cell phone chargers from goodwill for all my projects. Test it with a meter first to confirm it's 5 volts... Then enjoy!

Sure, but I would suggest including a fuse of some kind.

Just avoid older wall wart chargers that deliver their specified voltage only under their designed load. Under lighter loads their voltage is much higher. As bpowell advises, check the unloaded voltage with a multimeter before you use it to ensure that it has a true 5 V output under varying loads.

Ok, I will check chargers without load.
Two more questions:

- Why the fuse?

- Do I must cut the male connector ?
Do you know any practical way to avoid this?

You mentioned a wall charger 5V - 1000mA.
i.e. 1 Amp potentially. Posssibly more briefly with capacitance.

" Why the fuse?"
A circuit mistake by you or a careless moment could result in 1 Amp or more entering the circuit.
This could easily zap components.

A fuse (or some breaker) could provide some protection.
A little circuit might be saved with a 100mA fuse, for example.


"Do I must cut the male connector ?
Do you know any practical way to avoid this?"
- Well, obviously if you can find the corresponding female connector it would save you chopping it off.
Assuming you connect things correctly, it could also ensure the correct polarity of + and -.

I've cut the connectors off of my 5V power supplies and put on a 2-pin header...which is what I use on all my project boards.

One thing to check / confirm: Wire-color does not always make sense...I have seen RED as ground, and BLACK as positive...or I've seen White and Yellow wires...crazy...just meter it out, and mark your connector so you avoid reverse polarity.

I generally throw a diode on my project boards as well if I'm going to have plugable power...just to protect me from myself.

I wouldn't bother with the heavy chargers (the ones with a 50hz transformer in them), they waste a lot of power if on for a long time and may not be well regulated. Use a switch-mode supply (lightweight and very efficient) and it will be a well-regulated supply and quite possibly protected as well. Most likely an SMPS will be 5v but you can use a lower voltage (say 3ish) with a Picaxe quite happily if that is what you have. Recent ones will have the micro-usb plug so unless you want to use a similar socket (and are very good at micro-soldering) you probably will have to change the plug.

Once you reach the point in electronic knowledge where you are modifying consumer electronics you will quickly learn that standards can not be counted on to be in place. I check everything against my meters and have done so for years. I measure resistor's values even though I know the color code by rote. I even check the polarity of diodes, having had to deal with a bag of them that came from the manufacturer with the Cathode band on the Anode end. Electronic circuits are like old-fashioned column addition. Just one small mistake and the final answer is wrong.

I got a batch of 3 watt LEDs not long ago - one of them was marked reverse from proper mark... however it did work...

John West said:

I even check the polarity of diodes, having had to deal with a bag of them that came from the manufacturer with the Cathode band on the Anode end.

Click to expand...

SunLed surface mount LEDs are famous for this. Some colors are marked correctly (pointed end of symbol to cathode), others the complete opposite. The data sheet shows the incorrect symbology correctly, though, so it's OK (according to them when I pointed it out). Does your head hurt yet?

And a Merry Christmas to all!

Rip

I once got some LEDs that had been made wrong - the flat spot was on the wrong side!

I got a whole pack of resistors that were backwards. What a pain!

pack of resistors that were backwards.

Click to expand...

Good one.!! Reverse polarity can cause havoc on old carbon resistors.

I presume the color bands might have been in reverse order rather than the carbon resistors being asymmetric in values... ya never know...

I'd never tried it.
What happens if I change polarity in a PICAXE?

coparu67 said:

I'd never tried it.
What happens if I change polarity in a PICAXE?

Click to expand...

It turns your project evil. DON'T DO THIS!

Interestingly (and surprisingly) it is possible for a PIC (in the form of a Genie) to survive reverse polarity, as I have seen it done amongst the GCSE electronics kids that I help out. But their projects are simple and only have to work once in sight of the teacher. How long it would work after such treatment is anybody's guess. The cause is generally soldering the chip socket onto the pcb the wrong way round and then not checking.

Rotated chips don't always create a true reverse voltage through the silicon due to which pins are used and internal ESD diodes acting as a bridge rectifier, keeping voltage the right way up as far as the silicon sees things. Sometimes one gets lucky.