Audio Phone Ring Generator Using Switching Supply

Posted on Feb 6, 2014

The telephone ring generator shown generates the bare aerial voltage from a simple switching approach ability accumulation (SMPS) which employs a CMOS Schmitt Trigger aboveboard beachcomber oscillator, 10 mH inductor, aerial voltage switching transistor (TIP47 or added aerial voltage, 1 amp transistor) and a disciplinarian transistor (2N3053). The

Audio Phone Ring Generator Using Switching Supply
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inductor should accept a low DC attrition of 1. 5 ohms or less. The switching accumulation charge accept a amount affiliated to anticipate the voltage from ascent too high, so a 22K resistor is acclimated beyond the achievement which banned the voltage to about 120 DC with the buzz ringer broken and about 90 volts DC connected. The achievement voltage can be adapted by alteration the amount of the 150K resistor amid pins 10 and 11 which will adapt the oscillator abundance (frequency is about 800 Hz as shown). The accumulation is gated on and off by a additional Schmitt Trigger oscillator (pins 12/13) so that the buzz rings for about 2 abnormal and again the ambit idles for about a minute amid rings. These times can be adapted with the 10K and 300K resistors affiliated to pin 12. The advance button apparent is acclimated to manually arena the phone. The 25Hz campanology abundance is generated by addition Schmitt Trigger oscillator (pins 1/2) which controls the H arch transistor achievement circuit. The 6 transistors in the achievement date (4 NPN, 2 PNP) should be aerial voltage types rated at 200 volts beneficiary to emitter or more. The ringer will alone draw about 10 mA, so the achievement transistors can accept a low accepted appraisement but charge accept a aerial voltage rating. I acclimated TIP47s and baby arresting PNPs of alien numbers that I had on hand, but added types such as NTE287 (NPN) and NTE288 (PNP) should...

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