Need High Temp Piezo Speaker

[bobledoux]

Anyone know of a source of piezo speakers capable of working at 125 degrees C?

 

[Sceadwian]

For what practical purpose? That's a really high temperature to want a piezo to work at.

 

[bobledoux]

I want to place a temperature sensor inside a hot air balloon. It would transmit data to the instrument panel in the basket. Because of the environment I suspect I will need to place all the components inside an insulated container. The container needs to protect the electronics for up to 2 hours. The sensor and PIC microcontroller are good to 150 degrees C. The battery is probably only good to 40 degrees C. If I use ultrasonic data transfer I suspect the transducer must survive in the heated environment. I want to use a 24Khz frequency, which is within the upper limits of some audio components.

I'm also not certain what insulator could be used for this application.

RF might also be an option.

 

[KMoffett]

Why no just use Mil-Spec plenum grade Teflon insulated wire?...good to 200°C...direct hard-wire power and communication to the sensors...no temp problem with batteries and controller in the basket.

Ken

 

[Sceadwian]

I'm with Moffett, finding high temperature insulation for wire running from a thermocouple would be far more practical that putting an entire wireless device inside the baloon, far far cheaper as well.
Where is your sensor located? I'm pretty sure there are some severe temperature gradients in a hot air balloon, what's the purpose of measuring the air temperature?

 

[bobledoux]

The standard technique is to run a Teflon wire pair up a fabric sleeve inside the balloon to a sensor. Some use an RF transmitter placed on the exterior with the sensor placed though a hole in the fabric.

I want to create an informal system that I can hang inside. I realize now that the temperature limits on the battery will be the limiting factor. Typically, the upper temp limits are 125 Celcius with a possible short period to 150 for a minute or less.

I'm now looking at an RF transmitter contained in an insulated case that will protect the interior from a 40 degree C temperature rise over the course of 90 minutes. So I want an upper limit of 60 C on the interior while the exterior sits at an average of 110C.

 

[Sceadwian]

You haven't said why you're trying to do this instead of simply placing the a thermocouple in the baloon at the location you want and running wires? It's far simpler, far cheaper, far more reliable. You're going to have to suspend the device in the baloon somehow anyways wire will work fine and then you don't have to put any electronics on the inside of the balloon itself. Good luck finding something that can survive a 40 degree C rise over an hour and a half, the entire idea seems just this side of absurd considering a superior simpler cheaper way of doing it is already available. What do you think to gain from the method you're looking into? I can see absolutely no possible benefits and nothing but downsides and reasons not to do it.