# The story of the Evil Wall Wart!.

Hello,

Im building and sound synth with an Arduino, for that task I chossed a well known PSG. The thing is this chip needs 12Vs, and the arduino of has a max (regulated) voltage of 5.

So after reading specs on this IC, plus many feedbacks of people trying to achieve the exactly same as me, most (or all of them) recommended me to NOT use a Wallwart, since most them could short the PSG if the voltage becaomes too high. So I have plenty of questions, most of them probably will sound silly, still your answers can help me to clear my problem.

1. I've read on some electronics-forums that is possible to build some sort of 5v to 12v converter, how could I achieve this? makes sense to fully power my project or powering the arduinos with 12v can make it unstable?

2. Another option I saw is to build a regulated-power-supply. (There is even some sort of guide which can help you to convert a ugly wallwart into a regulated power supply), any recommendations thoughts on this approach?

3. I have this ugly wall-wart, which I tested with my multimeter. The voltage never goes more than 12V (11.8V), how can I know if this wallwart its a switched mode (SMPSs) or not? how I can know (testing...)? I read somewhere that switchedmode wallwarts are not as bad as regular wallwarts,

1. any other recommendations alternatives?

According to the 6581 specs it needs:

Absolute Maximum Ratings:
Supply Voltage Vdd -0.3 VDC to +17VDC
Supply Voltage Vcc -0.3 VDC to +7VDC

whatever that means

cheers and thank yaa!!!

By looking at the pinout of the chip in question, you need 2 voltage supply. Because I see a gnd on the chip.

My guess is : Vdd = 12 V and Vcc = 5 V into the chip, and all gnd connected. That make sense.

Before you get too far, work out how much current you need to supply at 5V, 12V and any other voltages your circuit needs.

This will determine whether it's practical to derive any of them from each other using converters/regulators.

If you can't tell what sort of wall wart you have from the label/brochure, you might be able to guess from the size. Most 50Hz transformer based wall warts are huge (even quite low current ones). On the other hand, a 1A switched mode power supply could fit within a standard UK plug. (If you aren't UK based that might not be much help.)

Actually I do have the that wallwart specs, its a variable voltage (configurable voltage thru a pot 5v-6v-6,5v-9v-12v) wallwart

Input 100-240V 50-60 Hz 6000mA
Output 5V 3,3A - 12V 3A

Im in spain, as said I tested the output of it, while set to 12V, and I throwed me 11.7, My scare is if I can trust this voltage to be stable or not?

There are regulated wall warts (available as both "linear" and 'switching" designs).

Or you can get an unregulated wall wart and run it into a regulator. For low current applications, a simple 3-terminal linear regulator such as the [u]LM7812[/u] is easy to use. You do need to feed-in slightly more than 12V, because there is always some voltage drop acrosss the regulator. Switching regulators require a few more components (including an inductor), but they are more efficient.

1. I've read on some electronics-forums that is possible to build some sort of 5v to 12v converter, how could I achieve this?

There are step-up/step-down switching regulator chips or you can get a DC-to-DC converter module that does it. But, i only recommend it when there is no eaiser way. (I'm using a DC-DC converter module for an automobile project that needs +/-12V.)

Input 100-240V 50-60 Hz 6000mA

The fact that it runs on 100-240V indicates that it IS a REGULATED switching supply. You'll be safe... as long as nothing goes wrong with it.

The 3 Amp output rating is also an indication that it's a swtching design.

and I throwed me 11.7, My scare is if I can trust this voltage to be stable or not?

Less than 12V is another indication that it's regulated. Typically, an unregulated supply will put-out (approximately) it's rated voltage at the full rated load (3A) and more (maybe as much as 18V) with no load.

Thank you so so so mu Doug! Ill continue my project more with more confidence!