Charger – battery compatability

For a project this set-up was bought:

It consists of a Polymer Lithium Ion battery (3.7V) with a capacity of about 400 mAh and a LiPo Charger Basic – Mini-USB.

Now, for another project we have a Li-Ion recheargable battery, 3.6 Volt
(for example this one)

Now, the question is if the button cell battery can be charged with the LiPo Charger Basic?

Codes, colours and conventions

When you open up an electronic device, you are confronted with quite a lot of colours on the components (especially when the device has a certain age – smd components unfortunately are less colourful).

“The electronic color code was developed in the early 1920s by the Radio Manufacturers Association (now part of Electronic Industries Alliance (EIA)), and was published as EIA-RS-279. The current international standard is IEC 60062.

Colorbands were commonly used (especially on resistors) because they were easily printed on tiny components, decreasing construction costs. However, there were drawbacks, especially for color blind people. Overheating of a component, or dirt accumulation, may make it impossible to distinguish brown from red from orange. Advances in printing technology have made printed numbers practical for small components, which are often found in modern electronics.”

Resistors, for example, have three bands of colour indicating their value in Ohm – the fourth band indicates how accurate these values are. Knowing their value is essential, even already for basic electronics, because they control the voltage passing through your electrical circuit.
You can learn the values of these colours by heart, or you can use little helpers, who come in several shapes and sizes.

– There are lots of online resistor calculators

– I’m quite a fan of this resistor calculator:
cardboard resistor calculator

– There are good looking apps, such as this ElectroDroid.

When you use leds, having the right resistor at hand is very necessary, because when it gets too much power it stops working.
So, of course there are online calculators for leds!
Even thermistors have their own calculator.


From Arduino (5 Volt DC) to 220 Volt AC

For quite a few of the Ellentriek#11 projects, participants wanted to connect Arduino to the main current system: 220 Volt.
As this can be tricky, it’s good to look for solid solutions.
I have found a relay set-up which is safe to use with 220 volt and arduino (yeay!).

This is the little board:
and you need of course to add all the components. The transistor and diode are essential for safety (making sure that the current only goes into one direction).

There is a tutorial on how to build it:

I buy all my Sparkfun stuff here, which makes sure that you avoid the international shipping costs and the US taxes.

(I got the relay specs here)