Do you know that almost every house has a free electricity source? Yes that is true! No bills !
This short post will show you how to find that free secret source and make use of it. But first let me ask you this question: Do you know how a telephone works? If no, please click here for more details.
In summary, telephone lines at homes connect to the telephone network using two wires called Tip and ring. Usually the tip is green colored and the red is ring and these wires are connected to the telephone company and used for all the communication between users. They have limited bandwidth and carry a permanent 48VDC and temporary 40VAC to 70VAC that only occurs when the telephone line rings. Maximum electric current that can be drawn from the wires is almost 50mA, and both the DC/AC voltages are supplied by the telephone company using special batteries and AC sources. So the DC voltage is available at home 24/7 and AC is only there when your phone rings!
With this in mind, why don’t we use this 48VDC of the telephone network at homes to operate some simple electronic devices? So can we consider this telephone line as a “free” hidden electricity source? Of course we can! so any house with a telephone line can be used as a free electricity source with some limitations on voltage and current. Remember current is limited to around 50mA and voltage to 48VDC. So now let’s build a simple circuit that converts or limits this voltage to say 5VDC and use it to power a simple LED lamp. Keep in mind that if a telephone rings then a 40-70VAC will occur on the line, so we must protect our DC circuit and convert this AC into DC. Let’s watch this tutorial:
I think the video is clear, it shows a simple circuit which consists of two main components: a bridge rectifier and a voltage regulator interfaced with a telephone line. These two components will make use of both the AC & DC voltages and power a LED lamp. Circuit schematic:
Here are some tips:
- 48VDC can be changed to a lower DC voltage according to your design using any voltage regulator . You can use this link to find out more
- AC voltage will be there when telephone rings, so we should use a bridge rectifier to convert this AC to DC. To buy a rectifier click here
- Safety first!