so far no schematic I've seen has the components available at JLCPCB : (
EDIT: the components missing are the ones I need to design a step-up boost converter to power the atmega328p from one AA battery.
How do people go about stuff like this? am I setting my first project level just too high?
Thanks for any help or advice you guys can give!
Andrea
JLCPCB certainly has the ATMEGA328P-AU chip (currently showing 2618 parts at $32.9ea!) and plenty of SMD resistors and capacitors of various values.
If you want to use a single AA battery to power your 328P, then I suspect that you will need to include some sort of voltage booster circuit as the 328P is spec'd down to 1.8V in the datasheet I am looking at.
thanks for the reply @TomGeorge and @markd833 , and sorry I should have been clearer!
My struggle is with designing a surface mount step-up boost converter to power the atmega328p.
I'm a skilled software developer and I can do simple bread board projects (I have my atmega328p running standalone already), but I'm totally inexperienced on pcb design and electronics in general.
The boost converter projects I see around (sparkfun, pimoroni) all have at least one or more components I can't find around.
Right from the start, I’m concerned about what else is on your PCB…
Whatever draws any current in your design needs to considered. in your power budget.
‘Boosting’ the voltage from a single cell introduces other issues - as the ‘power’ you can draw over time is a combination of voltage, current, losses etc.
Your booster single cell could last anything between a couple of hours, and a couple of weeks (or no time at all) - depending on software design, CPU clock speed and peripheral utilisation.
It’s quite possible you may need higher energy density
(like a lithium cell) to achieve a practical operating life and perhaps optional recharge ability.
Unless you absolutely must have the boost converter as part of your main board, then I would suggest using an off the shelf module.
I've only done it once - for a battery powered device (2x AA) and I used a TI device. I stuck rigidly to the manufacturers suggested PCB layout, as @TomGeorge also suggested. The design worked perfectly for the second batch of boards - the first batch of boards got a polarised capacitor the wrong way round due to a cock up with the board manufacturers pick & place machine!
yeah it sounds like this might be too much for a starter project.
Here's the thing, I'm designing a little synth kind of device, eventually I'd love for people to be able to buy it preassembled and have very small batches made by manufacturers.
Would it be easier if I had a 9v battery and used the arduino uno power schematic?
Those 9V PP3 batteries are useless. I would stay clear of them. If you want to go battery operated, then I would also stay away from an UNO type design. Have you thought of using something like an Arduino Pro Mini? You could create your own PCB to take one of those as a plug in module.
one of the requirements for this project is to have a single pcb that needs to look fairly clean. There's not going to be any enclosure, similar in spirit to a Teenage Engineering Pocket Operator.
Ok, so if it has to be a single PCB, then have a look at the OnSemi device that @johnwasser suggested. The datasheet for it is here:
Page 9 of that datasheet has some nice single sided layouts for buck or boost layouts. The layouts are for the DIL package whereas the JLCPCB device is a SOIC package, but I think the pinouts are the same for both packages.
the MC34063A looks great, the doc says "Operation from 3.0 V to 40 V Input", so I guess this can work with two AA batteries?
Also says the output is adjustable but I'm not sure how I'll get 5v from the diagram they show (sorry again for the total newb questions!).
Can you expand on your project. What other components are there? Maybe an LCD, or an OLED etc.
What voltages do these require?
If you are looking at 2xAA, then depending on your hardware needs, you can run directly from the batteries without any additional power supply circuitry.
You might consider a Li-Ion battery. A size 18650 is 3.7 volts and slightly larger than a AA alkaline. You would not have to have any up-converter and you will have longer run time (as the 18650 can be had with more energy than a AA alkaline.
In addition, you will not have the losses associated with an up-converter. You would be lucky to get 85% efficiency with such a low load current.
That is not at all a beginner project. Buy a professionally designed, tested and fully characterized boost converter module and plunk it down on the board. Pololu has an excellent selection, and most are as compact as they possibly can be.
I'll need this to run at 16mhz and have audio output from a headphone jack plus three leds to be powered on at all times. From what I gather having batteries without any regulator will just mean that as they deplete the current will change. I'd rather have the device not powering once the capacity of the batteries drops under a certain threshold.
Anyhow, it is looking like this might just be a rather long journey, I'll start with a simpler design as suggested, either integrating a pre-made boost converter or an entire arduino nano and then see it from there. Hopefully I'll learn what I need along the way to then do an entirely custom board from scratch.
16mhz is only because I'm assuming that I will need that to use an audio synth library called Mozzi.
As for the audio jack, I will for sure need out, ideally I'll also have an input jack too to chain this synth-toy with itself.
