BIG electrical problem with Arduino UNO and wall Transformer at 230V

Hello,

I have a KUMAN Arduino Uno which needs to be powered by this transformer.

Consider that on the board I have uploaded a firmware that correctly works with a general 9V battery. My firmware have a section for microSD writing and with the general 9V battery it correctly works.

The problem is that when I cut off the general 9V battery and I put in this transformer, the board's light turn on but the microSD do not write and give me a flashlight as "error alert". I am sure that there is an electrical problem, so. Can you explain to me HOW I need to connect the transformer to the board in order to have the normal functioning as results (just like the one I have when the general 9V battery is connected)?

Please help me as soon as possible, thank you very much.

Hi,

I cannot give you a definitive answer. But the transformer you specified appears to be for halogen lighting. There is no reason to believe the output is pure DC. It could be (and probably is) some type of AC waveform. I ran into a different brand of halogen lighting transformer some time ago and the output was not even close to DC**.

Now I expect you might ask how to convert the output from whatever it is to DC. I can guess but I would really have to know more about the actual output waveform.

** the 9V battery is pure DC and the Uno requires (almost) pure DC.

SimonCa:
Hello

Hello there. My recommendation is to not tinker with power mains electricity components if you don't really know what you're doing. In your case, you not only didn't know what you were doing, but you also went ahead with just connecting something together (with no understanding of it).

JohnRob is right. The transformer you have converts AC power mains voltage to a smaller AC voltage, for powering lights that work with an applied 12 volt AC voltage. Not DC.

What you need to use is a regulated DC power supply, such as a 9 volt DC power supply. This means..... don't use that transformer. Use something appropriate...... which will be a 220 volt AC to a DC voltage converter device.

Hello both, thank you for your feedback.

Can you suggest to me what can I do now to convert the AC output of the transformer into the DC output that I need? What piece can I add to the circuit?

Thank you very much.

You'll need a diode (or full-wave bridge rectifier) and a capacitor. [u]Here[/u] is some information I just found about building power supplies. (I've built lots of power supplies, but I just did a search to find some sample schematics.)

The capacitor will charge-up to the AC peak which is about 1.4 times the RMS voltage. So a 12V AC transformer will give you about 17V DC. You'll get a 0.7V drop across a single diode, or twice that across a bridge rectifier. But with a light load, you'll probably get more than 12V out of the transformer so I wouldn't be surprised if you get 20VDC. Do you have a multimeter?

You may need to build a "DC condom". Input power plug that fits the AC adapter plug you are using, a full wave rectifier (or 4 diodes), a decent sized electrolytic capacitor to convert AC to DC and filter out ripple, then the output plug that is 5.5mm and 2.1mm that fits standard Arduino power plug. The condom will also work if you have a DC adapter with correct sized plug but has reversed polarity.

SimonCa:
Hello both, thank you for your feedback.

Can you suggest to me what can I do now to convert the AC output of the transformer into the DC output that I need? What piece can I add to the circuit?

Thank you very much.

No, that's not the way to go, you seem fixated on using an unsuitable component for the job.

Much simpler to power the Arduino from a suitable regulated DC power supply in the first place,
such as a good quality USB supply - you even have the right cable for this already...

Also I suggest getting a cheap multimeter with DC and AC voltage ranges before doing anything
else to avoid expensive errors like this. If a power source gives out any AC voltage its not a
regulated DC supply and not safe for the Arduino.

Solved.

Thank you, we can delete the post

Hi,
Do not delete the post, as others may have a similar problem

I have uploaded a firmware that correctly works with a general 9V battery. My firmware have a section for microSD writing and with the general 9V battery it correctly works.

What firmware?

Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html then look down to item #7 about how to post your code.
It will be formatted in a scrolling window that makes it easier to read.

How are you connecting the 9v to the Arduino?

Tom… :slight_smile: