Hello,
I am using a 2.1mm power barrel jack with switching (of battery), plus 9V battery. The power supply input would be 7-9V with a positive center plug. Would be appreciated if someone could check over my schematic.
(Arduino Nano v3).
Sincere Thanks,
TonyAm
That should work but be careful, as the battery discharges the MOSFET will get into the ohmic range and start dropping voltage and getting hot depending on the load. It appears you read some data sheets and have the necessary capacitors in front and behind the regulator:-)
Thanks. Yes, the MOSFET did get warm on another circuit that included an LCD. Anyway to fix that (and still use the MOSFET), maybe a MOSFET with higher voltage handling?
Thanks again,
TonyAm
I don't think that would help (might even make things worse).
Why are you building this circuit? Nano has a built-in regulator which is enough for its own needs and a little more for external circuits.
A better solution could be a DC-DC "buck" regulator, which will be 80~90% efficient, compared to the 55~70% efficiency of any linear regulator with these voltages.
Best of all, a 5V power supply.
Thank you. Yes, I can see how it would make things worse, (using a higher voltage rated MOSFET).
The circuit in question doesn't use an LCD, so I digress (its not over heating).
This circuit powers a simple audio synthesizer circuit using the Mozzi Synth library. Nothing is heating up on this circuit, (but did on a previous one with that included an LCD). I think I understand why now.
When making circuits with Arduino boards in the past I have had power problems when adding other peripheral components. Until I started using a power configuration told to me in this forum. Where I power the Arduino chip with 7-9V using the Vin pin, and then powering peripheral components with a regulated 5V from a 7805 chip.
I'll post my schematic tomorrow in case it might help or be of interest.
The Buck regulator is very interesting, something I have read about, and might use in future circuits.
Sincere thanks for the help.
TonyAm
Larger LCD like 20x4 character or 128x64 graphic often have backlights that need quite a lot of current, 80mA would not be unexpected. By comparison, the Nano itself probably only requires around 20mA.
I guess maybe in audio synthesiser circuits, care must be taken when using DC-DC buck or boost converters, because the converter's oscillator frequency, or harmonics of that frequency, could leak out into the rest of the circuit and be audible.
Yup, that's what I used, the big 20x4 character/w backlight. The MOSFET got warm. I'll keep that in mind, concerning the possibility of the Buck converter's frequency interference.
Much thanks for that. Appreciated.
TonyAm
Make C5 larger, at least 10uF
What is the part number of the MOSFET?
You have the right area but on the wrong pins. You need a lower Vgs (Voltage gate source) part. This determines when the part conducts, the higher the voltage the higher the drive voltage you will need. Try to use something in the 3 Vgs range if you can, it will stay cooler.
I am using IRF5305 IRF5305PBF Power MOSFET P-Channel 31A 55V. I'll attach the datasheet.
Thank you.
P_ChannelMOSFET_A-4604.PDF (182.8 KB)
In case anyone might be able to proof read the whole schematic I'll include here.
It uses the Nano v3 and utilizes the Mozzi audio library, currently the schem shows PWM output at D3, however there will also be a an output for D9 (for the Mozzi library).
If it's available to you the AOI21357 would be a better choice
Digi-Key has them
What is the purpose of the Mosfet?
The MOSFET is just acting as power polarity protection, in case someone uses the wrong kind of plug, in this case a negative center plug instead of a positive center plug. There are other ways to provide polarity protection, such as with a diode, but I thought the MOSFET solution was really cool.
Thanks for that info, I appreciate it. I will check that out.
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