Brigadoon - An Occasional Corner on the Internet
The devices that are used on this site are normally required to either work from a mains supply or from a +12V battery such as the domestic battery on a houseboat. For many commercial devices, the normal supply voltage is not +12V, it can be lower, such as +5V or +3.3V, or it can be higher at +24V. While this is relatively easy to accommodate when the primary power source is the mains, it can be harder when the primary power supply is a +12V battery.
Switched-mode DC-to-DC converters convert one DC voltage level to another, which may be higher or lower, by storing the input energy temporarily and then releasing that energy to the output at a different voltage. The storage may be in either magnetic field storage components (inductors, transformers) or electric field storage components (capacitors). This conversion method can increase or decrease voltage. Switching conversion is more power efficient (often 75% to 98%) than linear voltage regulation, which dissipates unwanted power as heat. For example, a linear power supply outputting +5V from a +12V input is, at best, only 42% efficient.
D.C.to D.C. Converters
Designed by Mark Little
For devices installed on our houseboat, efficiency is a major consideration, as the +12V domestic batteries are only charged by solar panels. As a result, it is highly desirable to power devices running from a +5V supply using a +12V to +5V DC-to-DC converter. As with many electronic items today, it is usually cheaper to buy a ready-made commercial device than build one yourself.
As a result, items such as the weather station on the houseboat is powered using a commercial DC-to-DC converter.
One of the potential problems with DC-to-DC Converters is that they use fast switching waveforms to convert the voltages from one level to another. The can lead to R.F. Interference that can play havoc with radio receivers, especially when using the AM bands.
Filtering can be applied to the input of the DC-to-DC Converter to prevent R.F. Interference running back down the +12V supply lines and getting into other items power by the +12V supply. It is also probable that the interference will come out along the output terminals and get into the devices connected to the output of the converter.
NOTE: The model shown above, while cheap and reliable under most circumstances, is susceptible to failure in high temperatures. Our houseboat can get very hot (40~50+°C) if locked up during Australian summer heat waves. Two of these units have failed, one during a summer period and the other during the summer period the following year.
KREE DC/DC Converter
JIELAITE DC/DC Converter
Given the high temperature issues with the unit above, this unit is being trialled as a replacement to keep the houseboat weather station working during summer heatwaves when the boat is locked up. Various options will be trialled, including mounting on a heatsink and installing under the houseboat near the waterline where it is much cooler, which should test whether the unit really is waterproof.
It must be said that these options were not explored with the units above, so they might benefit from the same treatment.