Ok, so I buy two Chinese bike horns on ebay. One has a brand name of "RockBros" and another that's generic but identical to the RockBros model.
Originally, I was going to start this topic in our uC section for those that may be interested in doing what I plan to do. That being,.. replace the uC with my own that contains my own program. This is because I only like 1 of the 5 programmed sounds that they provided.
Fast forward: I decided that I needed to reverse engineer the circuit so I could can replicate the PIC pin-out and program my PIC accordingly. I've attached my reverse engineered schematic and photos of the board, so give them a peek.
Take note of the Piezo driver circuit Q1 and T1. T1 is a step-up auto-transformer that increases the audio output voltage to the Piezo. Nothing really odd there except for the fact that the audio signal from the uC will be a digital signal with fast rising and falling edges. This is what's got me scratching my head, as I don't see anything in this circuit to protect Q1 (or any other component) from back EMF that T1 will certainly produce.
Admittedly, I have not scoped this circuit as yet. Hopefully, doing so may bring some enlightenment,.. like a protection diode integral to T1. Though, I would think that a reversed biased diode across Q1's collector - emitter junction would be where I'd put it.
Any thoughts?
Chris
Originally, I was going to start this topic in our uC section for those that may be interested in doing what I plan to do. That being,.. replace the uC with my own that contains my own program. This is because I only like 1 of the 5 programmed sounds that they provided.
Fast forward: I decided that I needed to reverse engineer the circuit so I could can replicate the PIC pin-out and program my PIC accordingly. I've attached my reverse engineered schematic and photos of the board, so give them a peek.
Take note of the Piezo driver circuit Q1 and T1. T1 is a step-up auto-transformer that increases the audio output voltage to the Piezo. Nothing really odd there except for the fact that the audio signal from the uC will be a digital signal with fast rising and falling edges. This is what's got me scratching my head, as I don't see anything in this circuit to protect Q1 (or any other component) from back EMF that T1 will certainly produce.
Admittedly, I have not scoped this circuit as yet. Hopefully, doing so may bring some enlightenment,.. like a protection diode integral to T1. Though, I would think that a reversed biased diode across Q1's collector - emitter junction would be where I'd put it.
Any thoughts?
Chris