uSupply USB - Snap Poll!

[EEVblog]

Laying out the next version of the "USB" uSupply now.
As the title says, should such a small and low powered battery powered USB supply bother having serial comms capability via USB?
I know it would be kinda cool to have PC control, but without including it, the micro is 2/3rd's cheaper (due to lower pin count package saving), and no need for the optocouplers etc. How many people would actually want to PC control a little rechargable PSU? (Any bench version would definitely have it of course)
Still need isolation for the USB charging though, so I know what people are thinking - it has a USB connector, it has power isolation, so why not include comms as well?

NOTE: I am not talking about the bench version of the uSupply, this is the smaller pocket size USB charging version.

Many will be happy to know the latest design has dual LED displays and dual knobs like on old proto I have showed off. And uses an 18650 battery.

Dave.

[JoannaK]

Whatever you choose, there will be     

[mdev]

maybe two versions: one without the serial, and one with serial but without user interface, ie, screen and knobs, intended to be used with a terminal

[EEVblog]

Whatever you choose, there will be     

Ain't that the thruth!
I'm the only one stupid enough to ask these things 

Dave.

[Torrentula]

Whatever you choose, there will be     

That and I don't see the value it adds to the product if it's only charged by USB, plus it is really easier and faster to turn a knob and read a display directly on the supply instead of having to type long command strings into the terminal.

It's a power supply, I want a voltage setting and a current limit setting and not remember bloody commands

My two (hobbyist) cents,
Elia

[JoannaK]

Whatever you choose, there will be     

Ain't that the thruth!
I'm the only one stupid enough to ask these things 

Dave.

No. I'm quite sure a lot of us know the warm and fuzzy feeling. 

[Bored@Work]

There are advantages having a remote controllable PSU. E.g. logging current consumption of some device or driving a device with a particular voltage function.

The thing is does the feature increase or at least not decrease the overall profit? To answer that you have to estimate. Are people willing to pay extra for that feature? If not, will the feature sell more PSUs, at reduced margin, but in total at more profit?

I don't think the poll will answer such questions.

[Smokey]

Put the footprints on the PCB but omit the parts for a cheaper version.  You can even use super small more expensive parts since they won't be stuffed for the mass produced version.  A lot of us are capable of soldering that in later if we want it. 
Or do a second plug in board with just header on the main board.  This way you can go the big company "optional extra" and sell the communications board for 1/2 the price of the whole unit.

[8086]

How about a self upgrade option? Leave unpopulated footprints and provide a BOM for the serial part?

[frank26080115]

Personally, I've already started laying out a version of the uSupply but with a ATmega32U4, so it will have USB by default. This is just for myself for fun and learning.

I plan on using serial commands to simulate a battery discharge curve, while logging current consumption. I need to characterize a SEPIC LED driver.

I don't quite get how USB and optocouplers are related.

Firmware update via bootloader is always welcome, I don't know how many times you'd need to do this for a simple power supply though.

[Smokey]

Or how about just putting some IR LEDs on the UART.  Make the spacing compatible with the cheapest adapter for some other commercial multimeter that has IR and you have a cheap option using an already existing IR-USB cable you don't have to design.

[mikeselectricstuff]

The only reason I can see to have an interface is for firmware upgrades, and even then possibly margnal - ISTR the concept was a simple, small general-purpose PSU, not a whizz-bang networked jobby...
After all It's just a ***ing power supply.....

[Teemo]

Many will be happy to know the latest design has dual LED displays and dual knobs like on old proto I have showed off. And uses an 18650 battery.

This is really good news if two knobs are back, I like it!

[EEVblog]

The thing is does the feature increase or at least not decrease the overall profit? To answer that you have to estimate. Are people willing to pay extra for that feature? If not, will the feature sell more PSUs, at reduced margin, but in total at more profit?
I don't think the poll will answer such questions.

Agreed.
And therein lies the rub, I have no idea.
All I know is that the cost of this thing has been creeping up and creeping up, which was against my original intention.

Dave.

[EEVblog]

The only reason I can see to have an interface is for firmware upgrades, and even then possibly margnal

Even if I add serial comms, I have no intention of adding a bootloader to allow firmware update via USB.

Dave.

[opticpow]

Even if I add serial comms, I have no intention of adding a bootloader to allow firmware update via USB.

Dave.

Even though you're not adding the bootloader, someone else might being open and all. That said, I'd expect it on a bench supply, this maybe not so much. Would still be cool though 

Excuse me while I go extract the fence post 

[EEVblog]

Or how about just putting some IR LEDs on the UART.  Make the spacing compatible with the cheapest adapter for some other commercial multimeter that has IR and you have a cheap option using an already existing IR-USB cable you don't have to design.

That's not a bad idea at all.
But in the end, just saves a bit of cost on the chip.
Basically, I'm paying almost 3x the cost on the micro by having serial interface. The cheap chip (ATtiny48/88) does not have a UART. The ATMEGA88 I was using does not have enough pins, so to go serial I'm forced to use the ATmega164A

Dave.

[8086]

Software UART?

[Lightages]

Keep it simple and keep the cost low. The original intent was to have a simple to use, low power, handy power supply for random use in the field. If someone needs a power supply that will have all the bells and whistles then they would already have known the need and have a more capable supply ready.

[EEVblog]

Software UART?

Ugly, but possible, if there were enough pins available...
it's one of those project when you don't need much processor grunt, but pins count. So you are forced to pay for a more powerful chip in order to get the extra pins 

Dave.

[mdev]

or some header for RX and TX; whoever want to use the software interface can plug an USB to TTL interface; and may even use the Arduino digital pins 0 and 1 too, without the ATMEGA

[Fsck]

I think the poll might be inaccurate if the price difference isn't too large.

[Spikee]

Dave just make a header for the cheap PL2303 FTDI adapters from ebay. They are like 1.7 dollars each.
Who wants serial buys one from ebay 

[EEVblog]

Dave just make a header for the cheap PL2303 FTDI adapters from ebay. They are like 1.7 dollars each.
Who wants serial buys one from ebay 

Not quite that easy, they aren't isolated.
The whole idea of this is to make it idiot proof by being isolated.
I think I'll just go for the bigger micro and leave the serial footprints unpopulated.

Dave.

[Harvs]

I don't quite get how USB and optocouplers are related.

I see no point of having a serial connection if it's not isolated from the supply output.  That isolation is just needed too often in a lab power supply.

Nope I don't really it being worth the cost, I'd never use the uSupply when in my lab, and I can't think of an application outside of the lab where I'd need PC control or data-logging.  As stated already, the lab supply would be a totally different kettle of fish and some sort of PC control would be must for me.