I have bought the Smart Home Kit from Europe.
I guess I need 2 of these devices to couple with the littleBits AC Switch
if you hover the mouse over the picture, you will see its label zoomed
Input AC110-120V 50/60Hz
Output AC220-240V 50/60Hz
and vice versa.
In spite of good reviews, I think the label is not clear. See this other product
Converts AC220-240 Volt 50Hz to AC110-120 Volt 50Hz
AC110-120 Volt 60Hz to AC220-240 Volt 60Hz
In fact, I guess to convert from one frequency to another, a more complicated apparatus is required such as
(see the first of the list which is rated to 100W as the previous ones)
I tried to understand what is the matter with these converters and found that we need to look at these formulas
particularly V=4.44*f*Bm*Ac*N*10-6 (with V equal to applied [usually primary winding] rms voltage) and the Power handling capacity section.
You should invert above equation: N = V/(4.44*f*Bm*Ac*10-6) and consider what said in this other forum
A 60Hz transformer used on a 50Hz supply will be slightly over fluxed and heat up a bit more.
that is due to f being 50Hz in Europe, i.e. lower than 60Hz, and Bm is consequently higher (a lower f would require a higher N which we can't fulfil in either the primary or secondary winding at a given primary to secondary voltage ratio).
Now read this other article
If you bring your electric alarm clock, assuming that it works on 240 volts, and set it at 6 pm when you check into the hotel, it will read only 11 pm when it is midnight, and only 4 am when it is 6 am. You will probably miss breakfast.
Therefore, not all appliances will be fine with a transformer which doesn't convert frequency. In case of a clock radio, I guess it is a bare electronics matter. But there might be other situations where the (electrical) load type (reactive or purely resistive) and design can make a difference.
Finally, don't forget the whole question is about power (handling/loss). See the above linked table about Core weight, gram / Current density, A/mm²
Power handling capacity of magnetic cores is affected by the required regulation, copper space factor and temperature rise limit. The permissible temperature rise depends upon current density, flux density, frequency, class of insulation, duty cycle and the heat dissipation capability of the transformer. That is why power rating cannot be specified precisely.
This is the reason why transformers/converters are limited in power and also why you will need the power rating of the transformer (before any frequency conversion) to be a bit oversized by design to avoid converting frequency at all without harm.
Maybe other more knowledgeable people can provide more insight because there is actually more on this topic such as the difference between traditional transformers and those working in switched-mode (internally operating at several kHz but still outputting a seamless 50 or 60Hz voltage).