Hi,
I'm trying to build an LED brightness control and I'm basing it on the LED flasher at http://www.wrighthobbies.net/bots/lamp/index.htm.
I've looked at the schematic (http://www.wrighthobbies.net/bots/lamp/lampschem1.jpg), but there are no values given for transistor Q1 which is regulating the LED brightness by pulse width modulating the LED common ground of the Darlington transistor array.
I would be very grateful if someone could suggest a suitable value for Q1 and also which diodes D6-D10 I should use (are the diodes necessary). I'm using an Atmel AVR Mega16 which can source and sink 20mA. I can drive the ULN2003 from 5V or 12V.
I'm also trying to regulate the volume of a piezo buzzer - all I can think of at the moment is connecting the buzzer to the Mega16 via two different value resistors to control the PWM level, giving me two volume levels. Is there any more elegant way I can do this?
The piezo buzzer sounds fairly horrible - without going to a full blown sound synthesis IC, are there any other low cost methods I could use for generating a more pleasing beep?
Many thanks,
Richard
I'm trying to build an LED brightness control and I'm basing it on the LED flasher at http://www.wrighthobbies.net/bots/lamp/index.htm.
I've looked at the schematic (http://www.wrighthobbies.net/bots/lamp/lampschem1.jpg), but there are no values given for transistor Q1 which is regulating the LED brightness by pulse width modulating the LED common ground of the Darlington transistor array.
I would be very grateful if someone could suggest a suitable value for Q1 and also which diodes D6-D10 I should use (are the diodes necessary). I'm using an Atmel AVR Mega16 which can source and sink 20mA. I can drive the ULN2003 from 5V or 12V.
I'm also trying to regulate the volume of a piezo buzzer - all I can think of at the moment is connecting the buzzer to the Mega16 via two different value resistors to control the PWM level, giving me two volume levels. Is there any more elegant way I can do this?
The piezo buzzer sounds fairly horrible - without going to a full blown sound synthesis IC, are there any other low cost methods I could use for generating a more pleasing beep?
Many thanks,
Richard