Hello,
You'll have to forgive me, I hope I'm not asking too much, this is my first circuit that is actually useful. I've simulated it in both the demo versions of ISIS Proteus and LTSpice with no issues at all, but I really would appreciate it if somebody here could take a look at the circuit to make sure I'm doing nothing too silly.
What happens is when the button is pushed down (connected to RB0/INT pin on uController), it outputs high on RA2 and RA3 and so should close the relays, otherwise a low is outputted and the relays are opened. Just a couple of notes:
1) I'm having to simulate the player with a resistor. The player needs 3.7V and pulls typically between 50mA and 100mA (I can't find out exactly so I went for an average of 75mA), so I calculated the appropriate resistor with: \(R=\fra{V}{I} = \fra{3.7}{0.075} = 50\Omega\)
2) The relays have the following properties:
3) The resistor in the power terminals circuit connected to MP3VDD is there to (obviously) reduce the voltage applied to MP3VDD (which should be 3.7V rather than the 4.5V that would be supplied without the resistor).
4) As I say I've ran power terminal circuit through LTSpice swapping the terminals for resistors to simulate the loads, and I have the following:
uController current: 100uA
uController dissipation: 450uW
MP3 resistor current: 73mA
MP3 resistor dissipation: 59mW
MP3 player current: 73mA
MP3 player dissipation: 272mW
Speaker current: 500mA
Speaker dissipation: 3W
(V1, V2, V3) current: 573mA
(V1, V2, V3) dissipation: 860mW
V4 current: 500mA
V4 dissipation: 750mW
I think this all seems in line with what is expected. The circuit won't actually be on for more than perhaps 2-3 minutes every day, but I'm after fairly high capacity 1.5 batteries so it can last as long as possible, can anybody recommend a decent type?
Thanks,
Gump.
Edit: Sorry, just to say that the player on the circuit attachment is still 50Ω, this should be 75Ω.
You'll have to forgive me, I hope I'm not asking too much, this is my first circuit that is actually useful. I've simulated it in both the demo versions of ISIS Proteus and LTSpice with no issues at all, but I really would appreciate it if somebody here could take a look at the circuit to make sure I'm doing nothing too silly.
What happens is when the button is pushed down (connected to RB0/INT pin on uController), it outputs high on RA2 and RA3 and so should close the relays, otherwise a low is outputted and the relays are opened. Just a couple of notes:
1) I'm having to simulate the player with a resistor. The player needs 3.7V and pulls typically between 50mA and 100mA (I can't find out exactly so I went for an average of 75mA), so I calculated the appropriate resistor with: \(R=\fra{V}{I} = \fra{3.7}{0.075} = 50\Omega\)
2) The relays have the following properties:
although as the uController is running at 4.5V I am actually running under the nominal voltage but still well above the pull-in voltage, I'm assuming this will be fine.Part Number: EDR201A1200
Nominal Voltage: 5V
Pull-in Voltage: 3.75V
Dropout Voltage: 0.8V
Coil Resistance: 500Ω
Nominal Input Power: 50mW
3) The resistor in the power terminals circuit connected to MP3VDD is there to (obviously) reduce the voltage applied to MP3VDD (which should be 3.7V rather than the 4.5V that would be supplied without the resistor).
4) As I say I've ran power terminal circuit through LTSpice swapping the terminals for resistors to simulate the loads, and I have the following:
uController current: 100uA
uController dissipation: 450uW
MP3 resistor current: 73mA
MP3 resistor dissipation: 59mW
MP3 player current: 73mA
MP3 player dissipation: 272mW
Speaker current: 500mA
Speaker dissipation: 3W
(V1, V2, V3) current: 573mA
(V1, V2, V3) dissipation: 860mW
V4 current: 500mA
V4 dissipation: 750mW
I think this all seems in line with what is expected. The circuit won't actually be on for more than perhaps 2-3 minutes every day, but I'm after fairly high capacity 1.5 batteries so it can last as long as possible, can anybody recommend a decent type?
Thanks,
Gump.
Edit: Sorry, just to say that the player on the circuit attachment is still 50Ω, this should be 75Ω.
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