Wireless Piezo Beeper

The design utilizes a pair of 433MHz wireless modules that can be purchased pre-assembled, containing all necessary radio frequency components. These modules are integrated into two circuits: one for transmitting audio from the vario and another for receiving and reproducing it. It is advisable to construct the receiver first, as it can be utilized to test the transmitter circuit. The receiver circuit captures the radio signal and demodulates it into a signal that resembles the vario's audio output, which drives a piezo speaker located closer to the user's ear. When the battery is activated and no nearby transmitter is operational, the piezo should emit audible noise, serving as a straightforward method to confirm the receiver's functionality. Additionally, when the vario is powered off, the noise serves as a reminder to switch off the receiver battery. Veroboard is employed to connect the various components, with a specific layout utilized. A modified 2xAAA battery holder is used as the circuit enclosure, which is glued to the back of a 9V battery holder. Some helmets, such as the Icaro 4-fight, feature tail compartments that are suitable for mounting the receiver, allowing the piezo to be affixed to the receiver's enclosure. However, it should not be placed directly adjacent to the ear, as it may be excessively loud. The battery switch should be positioned in an accessible location on the helmet; if no suitable location exists, the receiver can be mounted on the harness, with the piezo connected via longer leads to position it near the head. The piezo should be audible if placed on the shoulder straps. This circuit modulates the vario audio signal onto a radio frequency signal transmitted through an antenna. The transmitter draws power directly from the vario's printed circuit board, eliminating the need for an additional battery. The power consumption of the transmitter is relatively low compared to that of the vario, so there should not be a noticeable increase in battery depletion. In fact, the vario volume can be set to its minimum once the wireless system is operational, conserving additional power. The transmitter circuit is designed to draw less than 10mA from the vario. Appropriate points on the vario PCB must be selected for the +BATT and 0V supply connections. The TXC1 wireless transmitter module requires a 3V power supply. Some varios feature 3V batteries, simplifying the power supply connection. In such cases, diode D1 can be omitted from the transmitter circuit. An example includes installing the transmitter in a Brauniger IQ Competition GPS, which utilizes 2xAA main cells and 2xAAA reserve cells. Other varios may employ different battery technologies with voltages other than 3V. It is essential to identify a suitable supply rail on the vario PCB for power connections. If a 3.6V supply rail is available, diode D1 should be included to reduce the transmitter voltage to the required 3V, as seen in the Brauniger Compeo (also known as Galileo) with a compatible 3.6V supply rail. If the vario lacks a battery or supply rail of either 3V or 3.6V, this design cannot be implemented as is; a 3V voltage regulator must be integrated into the circuit, or the transmitter must have its own battery. It is crucial to ensure that the supply connection points are selected so that the transmitter powers down when the vario is turned off, preventing battery drain between flights. The AUDIO signal should be sourced from a section of the PCB that drives the vario's piezo buzzer, without permanently disconnecting the vario's piezo, as it may still be needed in the future.

The design of the wireless audio transmission system involves several key components and considerations. The 433MHz wireless modules serve as the core of the system, facilitating the transmission and reception of audio signals. The transmitter module captures the audio output from the vario, modulating it onto a radio frequency signal. This modulation process is critical for ensuring that the audio can be transmitted over the airwaves without degradation.

In the receiver circuit, the demodulation process takes place, converting the received radio frequency signal back into an audio signal that can be played through the piezo speaker. The choice of components, including the piezo speaker, is essential for achieving clear audio reproduction. The placement of the piezo speaker is also crucial; it should be positioned to ensure optimal sound delivery while maintaining comfort for the user.

Power management is another vital aspect of the design. The transmitter's low power consumption allows it to draw from the vario's power supply without significantly impacting battery life. Careful attention must be paid to the selection of power connection points on the vario's PCB to ensure that the transmitter is powered down when the vario is off. This feature is important for preventing unnecessary battery drain.

The enclosure design, utilizing a modified 2xAAA battery holder, provides a compact and practical solution for housing the circuit. The integration of the receiver into a helmet or harness is facilitated by the flexible mounting options, ensuring that the user can comfortably wear the system during use.

Overall, this wireless audio transmission system is designed to enhance the functionality of the vario by providing a convenient and efficient means of audio output, thereby improving the user experience in various applications, such as aviation or other outdoor activities.The design is based around a pair of 433MHz wireless modules. These can be bought pre-built and contain all of the radio frequency components that we need. We use these modules in our two circuits; one to transmit our vario audio and the other to receive and reproduce it. It is worth building the receiver first because it can be used to test the

transmitter circuit. The receiver circuit receives the radio signal and demodulates it into something resembling our vario`s audio signal. This is used to drive the receiver`s own piezo which is located closer to our ear than the vario is. The schematic is shown below. When the battery power is on and there is no transmitter operating nearby, the piezo should produce some audible noise.

This is a simple way to test that the receiver is working. Also, when we turn our vario off, the noise reminds us that the receiver battery needs to be turned off too. Veroboard can be used to connect the various components. The layout which I use is shown here. I use a modified 2xAAA battery holder as an enclosure for the circuit and glued it to the back of a 9V battery holder as shown in this photo.

Some helmets like the Icaro 4-fight have tail compartments which are ideal for mounting the receiver. In this situation the piezo can be mounted on the receiver`s enclosure. It should not be located adjacent to an ear or it will be too loud. The battery switch can be installed somewhere accessible on the helmet. If there is no suitable place on your helmet it is possible to mount the receiver somewhere in your harness.

The piezo can be placed on longer leads if necessary so that it can be placed near your head. It should be possible to hear the piezo if it is placed on the shoulder straps. This circuit takes our vario audio signal and modulates it onto the radio frequency signal which is transmitted through an antenna. The schematic is shown below. The transmitter takes power directly from the vario`s own printed circuit board so that we don`t end up with yet another battery to maintain.

The power consumed by the transmitter is modest compared with the power consumed by the vario itself so you shouldn`t notice the vario battery going flat much faster than before. In fact you will be able to turn the vario volume to it`s lowest setting once the wireless system is working which will save some vario power.

The transmitter circuit should draw less than 10mA from the vario. Suitable points need to be chosen on your vario PCB for the +BATT and 0V supply connections. The TXC1 wireless transmitter module requires a 3V power supply. Some varios have 3V batteries so it is a very simple matter to obtain a supply. For these varios you should omit diode D1 from the transmitter circuit. An example is when installing the transmitter in a Brauniger IQ Competition GPS which has 2xAA main cells and 2xAAA reserve cells. Some other varios use different battery technologies which operate at voltages other than 3V. A suitable supply rail needs to be found on the vario PCB for the power connections. If a 3. 6V supply rail can be found, diode D1 should be included in the circuit so as to drop our transmitter voltage to the required 3V.

An example is when installing the transmitter in a Brauniger Compeo (aka Galileo) which has a suitable 3. 6V supply rail. If your vario doesn`t have a battery or supply rail of either 3V or 3. 6V, you won`t be able to use this design as is. You will need a 3V voltage regulator built into your circuit, or the transmitter will need it`s own battery.

Make sure that the supply connection points are chosen so that the transmitter is powered down when the vario is turned off, otherwise you will flatten your vario battery between flights. The AUDIO signal needs to be taken from a part of the PCB that drives the vario`s piezo buzzer. Don`t permanently disconnect the vario`s piezo in order to do this. After all you may still need it one day if

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