Earlier on in the week I picked up a UM3561 sound generator chip and I've since been happily making like an emergency services driver - albeit an American one - by hard wiring the select lines on a breadboard as per the following table:
S
n o V e
/ / s l Sel1 Sel2 Sound effect
c p s 1 ---- ---- ------------
--+--+--+--+-- n/c n/c Police siren
| | Vdd n/c Fire engine siren
| UM3561 C Vss n/c Ambulance siren
| | - Vdd Machine gun sound
--+--+--+--+--
V S O O (- Don't care.)
d e s s
d l c c
2 1 2
I'd now like to interface the device to my arduino, but I'm a little uncertain as to how to connect the select lines up and in particular how to effect a 'switched n/c'. I'd be very grateful if anyone can provide me with some guidance as to the preferred/easiest way to do it.
HI, looking at suggested circuits for this chip you can connect the sel1 and sel2 each to an arduino output, but make sure that the ground or neg of the chip is connected to gnd of the arduino.
If you have the chip using 5V then the logic levels from the arduino should be the same as VCC which will be a HIGH output and VSS will be a LOW output.
You may need to get a third output to switch a small relay on and off so that you can control if the chip is on or off.
Tom. 8)
I guess "n/c" is achieved by setting pinMode(INPUT); (without Pullup resistor )
You need to supply the speaker separately, but the chip's Vdd to switch the whole beast on/off can come from an Arduino pin as well as the sel1/2 pins.
( No relay needed )
According to this data sheet, it should be operated at 3V though, and the limits for HIGH / LOW signals are rather small ( 0.2V off Vss / Vdd )
Since its 3V you could try connecting the select lines each through a 10k resistor to an Arduino pin - this will
limit the current when the Arduino outputs 5V and hopefully it will work fine.
Thanks for the replies. I understand the potential issue in regard to the logic level, but I'm still a little unclear how to dynamically effect a 'n/c' state.
michael_x:
I guess "n/c" is achieved by setting pinMode(INPUT); (without Pullup resistor )
I hadn't thought of trying that. I did however consider using a tri state buffer, like a 74HC125, and have one arduino output pin to control the impedence and another to select high or low. Would that work OK?