DIY: How to get 110VDC from AC

Question

I am just getting into coils - I need 110VDC for some loud ringing apparatus. You'll have to forgive my inexperience. I'm very curious about best practices for making a long-lived transformer (possibly heatsinked if that's an issue). So two coils are needed, and what else? Google abounds with info, but I want to get the right parts and formulas and components off the bat, and also not die. The apparatus I need to drive is of the old PSTN type, which got its jolts from the landline. Thanks in advance, cluebats at the ready.

Answer 1

Another possibility is below with a small 10:1 transformer used as a stepup transformer. Choose cap RC time constant near 20ms for each half cycle or 25Hz, which is common for Europe. Then tune to get resonant frequency of spring toggle bell for max volume. This is fairly low current and turns ratio can be adapted to other supply voltages. EST. 1W max.

Answer 2

If the ringer is complete you should find a series capacitor in it to block DC. The ring signal is AC.

I agree with @PeterBennett. As far as I remember the ring signal was generated by a low-frequency alternator in the telephone exchange. It should, however, still work at 50 or 60 Hz. I suggest you try to find a transformer to suit your mains with a secondary of 30 to 100 V to test it out.

^{simulate this circuit – Schematic created using CircuitLab}

Answer 3

I have a copy of the ANSI T1.401.1993 handed to me personally by an active standards committee member back in 2004. I recall that the standard attempted to "cover all bases" with commonly found systems in the US, which themselves varied a lot. (It lists many dozens of systems that are specifically covered in the standard.)

Section 5.4.2.1.1 Ringing Signals: In most cases, the network shall provide an ac ringing signal between tip and ring at a frequency of 15.3 to 68 Hz with a voltage at the NI of 40 to 150 V rms. (A note says here that it may be as high as 175V rms in some cases.) The crest factor of the ringing signal will normally be between 1.2 and 1.6 and almost always between 1 and 2. The DC component, when supplied, shall be in the range from 0 to 105V (positive or negative.) On some lines with analog carrier systems, the ringing signal consists of 200V dc pulses applied between ring and tip, at a 20 Hz rate, and with a duty cycle of 50 percent. During the "off" period in these cases, a low resistance is provided between ring and tip to allow ringing capacitors to discharge. Note: The most common ringing voltage frequency is 20\$\pm\$3 Hz with an ac magnitude at the NI of 40 to 106V rms superimposed on a dc voltage of less than 80 volts dc. Newer network equipment produces a ringing signal with a frequency of 20\$\pm\$1 Hz.

The fact that there can be a significant DC component is interesting.

EDIT: I found this youtube link which describes the following circuit:

^{simulate this circuit – Schematic created using CircuitLab}

No indication about the exact transformer details, but it's not hard to infer them. It's not from AC here. I know that. Just thought I'd add this as a lark. There is also this EE.SE link to look at, as well. Finally, there is this HV430 datasheet to look at. Probably mostly unobtainium except for the fact that Microchip bought them up (and they support ICs pretty much forever, from personal experience.) You can buy one here.