What have you tried so far that didn't work?
How did it fail to meet your needs?
Which course is it for?

Mike Halloran
Pembroke Pines, FL, USA

A 40 Hz buzzer? What an unusual specification. Is that really what it needs?

If so, there should be a suitable driver (not transducer) available for it.

Mike, all odd questions aren't necessarily school work.

Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.

Off-topic (slightly): a major chemical complex near me used to run its distribution network at 40Hz until fairly recently. It was a legacy from the early days of the industry when plants used to generate their own power and there was no grid. Latterly, rotary frequency converters were used until these were finally retired. This part of England was an early adopter of industrial electrical power for mining and heavy manufacturing, and there were all sorts of little curiosities like the 40Hz system and true 2-phase distribution. Gradually the oddities are disappearing as standardisation continues.

Actually, I'm a antenna designer.The project is a buzzer array work on 40Hz. The passive electromagnetic buzzer should be drived with the external signal with 40hz 110V AC, and the preferred waveform is not sine wave but half square wave. The question is if the power is 60hz 110v AC, how do I change it to the working power for the buzzer.

Mike, I start thinking you may be right.

Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.

1: Use a VFD.

OR

2: Rectify it to DC, then switch it on/off. You may need to insert a transformer before the rectifier to get the output voltage correct. You'll need a solid state switch to live with the duty cycle.

You probably won't get square wave voltage with the buzzer connected, because its inductance will fight you. Of course, that's a guess, because you haven't told us squat about the buzzer, e.g., its DC resistance, current demand, power demand, whatever.

Mike Halloran
Pembroke Pines, FL, USA

I haven't see any commerial VDF change 40hz to 60hz, maybe it should be customized designed.
The total amount of buzzers is about 100 pcs. So the average power consuming maybe more than 300w, and the average current maybe more than 2.5A, the instantaneous current maybe higher.
Because the system is single frequency working, I'll try to conjugate match it.

• http://img.ddvip.com/2008_07/1216958178_ddvip_1859.jpg

Huh?

Mike Halloran
Pembroke Pines, FL, USA

Your signal diagram shows a popular method by which the AC creation stage of a DC-to-AC inverter works for taking two triange waves, one DC offset above the other, and using it to chop a low voltage reference sine wave into two PWM signals used to drive a H-bridge to turn a high voltage DC into a higher voltage AC signal. It still needs a low-pass LC to filter it. This is also the approach used for PWM sine-wave motor drives.

Now, if you need 40Hz at 115VAC, I suggest that you take a Variable Frequency Motor drive, and set it to produce 40Hz, or hack a true sine-wave analog-circuit inverter to substutue a 40Hz reference instead of the 60 Hz reference. You might also take one of the microprocessor-based AIMS inverters and substitute a crystal that is 2/3 the frequency of the existing crystal and get it to produce 40 Hz.