1 (edited by awalton 2006-08-31 14:18:56)

Topic: Power

What kind of battery is this thing going to have, and how do you plan on having the device charge itself? Will it have replaceable batteries or any kind of standard power connector to allow for external power (such as a wall outlet plug)? And, of course, as a hacker, I have to ask; will it be easy to split open and wire a new, more powerful battery to it as battery tech improves?

I ask because I already have many motorized projects in mind, and as we all know, motors use a great deal more power than processors. (My first reaction to the device as a whole was "Wow, it's the 21st Century Furby!, and I almost instantly conjured up ideas of it moving and shaking and possibly walking/driving around and my cats attacking it).

Thanks and Good luck!

FURTHER EDIT: The circuit below should not due to an oversight that causes it not to function properly with two cells. Please use it only as a reference for your own designs.

EDIT: Simple Lithium Ion Battery Charger circuit for Chumby follows
Changes for Chumby Daughtercard
Cells should be in parallel to be charged with this charging circuit, and as such only provides 3.7V, not enough to drive a(n) (Alpha) Chumby which requires about 6.5.
http://img409.imageshack.us/img409/3285/bc2ek2.png
BILL OF MATERIALS for changes
1     ADP2291     Analog Devices Lithium Ion Charger IC.     
1     BCPS1         Philips PNP Transistor (Max P. Dissipation @ 25dC = 1.3W, Beta @ 1A = 50, Vce(saturation) = 0.5v). Replace with any transistor that fits criterion for circuit ( ~0.7V Vce, .7W dissipation, 25 beta). See Analog Devices ADP2291 datasheet for details.
1     Small LED (blue for ChumbyRice smile)
1     100k resistor (optional, paired with thermosistor)
1     100M resistor
1     (330) resistor (any resistor suitable for controlling voltage for LED to prevent burnout)
1     10uF capacitor
1     100uF capacitor
1     470k thermosistor (automatic shutdown in case of battery overheating, optional)
2     LG 18650 2400mAh, 3.7V lithium ion cells, connected in serial, tabs on.
--Implementation #2 also includes
1     Schottky Diode (use an extra A240, 40V 2A diode like that of Chumby Mainboard)

Total cost: (pennies for resistors & caps + a few more pennies for the thermosistor + $1.70 w/ ship for one ADP2291 + maybe a buck for 10 of the transistors + ricer LED [you should have this laying around]) + 2 LG batteries @ $6.50/cell = approx. $15.

When the external power source is connected, the ADP2291 pulls some of the filtered (!!!!!!!!) voltage and uses it to charge the lithium ion cells. The chip is timed by the 100uF capacitor which automatically shuts the charger off when the battery's full, or after 3 hours, whichever occurs first. The device powers back on when the battery voltage drops by 150mV (and trickle charges to full, where it cuts off after 30 minutes). Like said above, the thermosistor protects the batteries from overcharging by cutting off the charger if the circuit gets too hot from the adjacent batteries (it reduces the power input to the batteries until a certain temp when the chip itself cuts off). The LED connected to the charge circuit tells us when the battery is charging.

If using a different battery (I actually changed planned batteries because of this), you MUST access the charge information of the battery. The circuit is designed around using these batteries and using different batteries (of greater, lower, or possibly equal power) will change the circuit. The ADP2291 datasheet has all of the information about choosing the right resistor (here played by the 100M ohm resistor) and the right transistor (here played by the PNP BCPS1) to match the batteries. It's also important to note that the transistor might get hot, so use wider traces on the PCB to soak up some of the heat.

Now, if only I had a Chumby to test it on... (actually, before anyone tests it out on a Chumby, it'd probably be smart to replicate the whole power circuit and try it on that alone to make sure you don't fry anything of real value. The ADP2291 is only a buck a chip (which is a lot to ask to be added to Chumby, but pretty cheap for a hobbyist) and if you're super kind the Analog Devices reps might even send you a free one or two. They're also teensy tiny buggers (3mm x 3mm) so use a pair of tweezers while soldering if you've got a free hand. Barring I did everything with my math right, the circuit should work fine. The biggest thing I can imagine that would go wrong would be the transistor burning out, but if that happens I'll let you know and I'll step up to a beefier switch. To the Chumbyista: this would be a nice addition that a lot of hobbyists might want, you might want to consider making a bit of room on the PCB for it if at all possible, it's only a few mm^2 :-D).

Future modifications include: Either adding a second A/D or removing the squeeze-o-meter/ambient light sensor and adding a battery voltage analog in for a battery-life meter. Using a digital input to indicate whether the Chumby is in battery mode or is plugged in (via the STAT pin on the LTC4412). (possibly) NiCad/NiMH charger for R/C car hobbyists.

Edit 2:
Second implementation is the quick and dirty move to the daughtercard as expressed by bunnie. Filter could be made better by adding a fuse to protect charging circuit and a R-C filter to clip out the remaining noise in the line. I'll be testing this circuit individually as soon as I recieve all of the components I need to do so (most are ordered, though it looks as if I'll have to pick up those diodes...).

Power-wise, in an ideal setting, 2400mA with a steady 200mA drain would last 12 hours, but reality is that the device would likely cut out at about 8 at best (peak power usage at 300mA, and capacity losses due to heat from all of the devices). It's worthy of noting the battery pack provides almost 4 times the amount of power as compared to the iPod 3/4G battery, but roughly 1.5x that of the 1st gen's Lithium Polymer battery. That being said, Chumby with a LiON pack will probably be hefty.

Re: Power

The deive normally operated from a standard 12V wall wart, but includes a 9V battery to keep the clock alive during power outages.  Under full load (display on and everything), the 9V battery lasts around half an hour.  The chumby can detect if it's running on the internal battery and currently shuts off most of the power-hungry hardware.

We made a "portable" chumby for Foo by connecting two lantern batteries to the main power connector.  We needed it to test the 14 or so wifi base stations we spread around O'Reilly's building for chumby users.  That will last a *long* time.

The wifi is on all the time.

Re: Power

I'd love to make my Chumby truly portable, but I don't want to fry the little guy. The web site's down, so sorry if you've already documented this, but any tips for hacking in a battery?

Re: Power

Yeah, we'll post something in the wiki.

bunnie is the expert on that sort of stuff.  He's on the road coming back from Foo.

Re: Power

Could you please tell us the average current consumption for chumby. If it's not too much trouble please post it for like Screen on, Screen off, Wifi On, Sleep mode (if it has one...), etc.
Also, how much capacity does the 9V batteries  have.
Thnkz

Re: Power

bunnie is the guy for that.

I'm not sure how useful that information is in the long run, since it would apply to these first generation prototypes and not necessarily indicative of the behavior of the production units, which may have entirely different hardware.

Re: Power

Ok, we'll have to wait for bunnie then... smile
I just want to know this for common knowledge of the hardware. I checked the schematics and it appears to me that this first generation chumby is quite hungry for Amps.

Re: Power

Yes - the goal of this prototype was to create a test platform, get it in the hands a few key people, and see what works and what doesn't work. This version was *not* about cost and power reduction - that's something probably for the third generation prototype.

We have a lot of work to do before the final production units.

Re: Power

You have to consider the size of the batt, the capacity, how to recharge it, and most important the price. These batteries tend to be on the expensive side

Re: Power

I might be wrong here, but I don't think a $20 battery has too much capacity. It would most probably be drained very fast. Usually highcapacity batts are in the range of $40-$100. Remember that chumby is mainly a clock and the battery has to last a very long time, otherwise it gets anoying to recharge batteries every 2 days... Once again this is just from what I remember and I may (and most probably) be totally wrong.

Re: Power

chumby is a bedside computer, so just run it off the mains.

if chumby takes a 12v input, does that mean it has a transformer in the plug or somewhere? and is it switching mode so it will take 240v aswell as 110v?

need upload space for the forums or a chumby blog? right here then
http://www.nophus.com/useru
username is chumby
password is chumby

Re: Power

According to the specs it chumby takes between 6 and 14V. If you look at the schematics there is no transformer. So there is a wallwart used for this purpose. Switching mode should be the smart way to go for any product that may be international.

Re: Power

Yes, there is a wallwart included with Chumby. It's an international-capable (110-240V, 50/60 Hz) device that outputs 12V @ 1A. It uses a P-5 style connector (2.5mm DC barrel connector) with a grounded collar.

Chumby consumes about 150 mA @ 12V idling, and this can peak to in excess of 250-300 mA depending on what you are doing. You can probably play a sound on the 2-W stereo speakers that drive your power consumption way up, but normally you aren't playing sine tones at full volume unless you are trying to annoy the heck out of everyone (oh hey, an alarm clock). Hence, the excess margin (1A) on the power input.

The best way to add a rechargeable battery is probably to look at the daughter card, not the core board. All of the important power supply wires are brought across the chumbilical to the daughter card, so you can add your charging control circuitry there.

Chumby doesn't have a battery in it because it has to be cheap. At $150 sales price, a $20 Li-Ion battery is a huge chunk of change for a device that really is meant to be plugged in and left alone. Also, optimizing for power consumption (such as using mobile SDRAM and improved switching regulators) costs money and we are literally shaving cents off the BOM at all corners to hit this aggressive price point.

However, it's open source so if you want to add a battery, be my guest. ^.^ I don't have to say I'm sorry for leaving that feature out, and I'd love to see the schematics when you're done.

7BAA 2E53 01C1 DCFF 497B  E7F0 9699 A303 78F0 D9B9

Re: Power

bunnie wrote:

Ultimate answer to life, universe and everything

Couldn't have asked for a better reply, thank you bunny!

Re: Power

Computer_Kid wrote:
awalton wrote:
bunnie wrote:

Ultimate answer to life, universe and everything

Couldn't have asked for a better reply, thank you bunny!

Lawl! :-)

Most remote control car batterys supply 9.6 volts at 350 mA.  It whould be able to keep it up for some time.  Why would wou want it complety wireless?

The real question is, why wouldn't you want it completely wireless? Unplug it from your nightstand in the morning and take it upstairs to the kitchen. While you make breakfast, listen to some music or catch up on some email or the latest Digg item or whatnot.

If you've got a road trip coming, download some maps from Google Maps into "ChumbyNav" and velcro it to your dashboard (or hook it up via cigarrette lighter and charge it). Play road games with the family. Review flashcards for a big presentation. Hook it up to the guts of your battlebot and you've got Chumby, Slayer of Machines. Hook it up to your Roomba and you've got ChumbyRoomba, the smartest vacuum cleaner ever (and quite possibly the coolest cat toy ever envisioned). Get a bunch of Roombas and Chumbies together and you could play ChumbyRoomba soccer.

It doesn't make the best portable device, so I wouldn't advise to toting it around like a PDA, but maybe with a revised case/shell (one with battery support and possibly housing for a stylus and a cheap CCD camera) and you've got a PDA-replacement.

The truth is, the board is small enough and the design is flexible enough that it can really be anything you put your mind into making it. All that's left is getting people's hands on it so that they can literally make it into those things wink.

Re: Power

well the chumby can last for an hour according to specs. so i shouldnt see why you couldnt pick it up, walk around for a bit, then dock it again. if i got hold of a prototype, id make some sort of a dock for it.

need upload space for the forums or a chumby blog? right here then
http://www.nophus.com/useru
username is chumby
password is chumby

Re: Power

I'm gonna have to build an external battery for this thing; I already have built two for my PDA.  Maybe I'll vacuum-form a cradle.  They say the battery doesn't last too long.

Incidentally, the clock-radio they show here is identical to my clock radio!
http://www.chumby.com/corporate/whatischumby
I have had it for 20 years, and it's still running, still keeps time and plays radio.  You would figure the electrolytic capacitors would have given out by now.  It would be nice to have something that can receive streaming audio, however.

Hack/Build/Make/Mod
Live.

70.80868%: Geek God.

Re: Power

That's cool to make it a standard 12v so that you can use 2 lantern batteries in serial for of the road. Perhaps a 12v car adapter would be nice too, so one can use the hotspots along the road, or in the parking lots of free wifi cafés, etc. smile

Re: Power

Personally, I wouldn't mind a rechargable battery even if I had to keep it in my pocket and have a wire running to it. As long as I can go somewhere and not have to plug it in :-D

Re: Power

jacubilloro wrote:

Ok, we'll have to wait for bunnie then... smile
I just want to know this for common knowledge of the hardware. I checked the schematics and it appears to me that this first generation chumby is quite hungry for Amps.

The 9V battery is rated at 570mAh (see data sheet here: http://rocky.digikey.com/WebLib/Panason … 04_v1.pdf)

According to our tests, the unit would be able to run for about 30 minutes with all the features turned on (the big power suckers are the LCD and WiFi dongle). However, we've enabled an "LCD mute" mode, so when the main power is removed, the screen will go blank and the chumby will enter a low-power state to ensure that the battery remains active for as long as possible (e.g., to still wake you up in the morning via the alarm). So, if you want to run on the backup battery only, you'll probably have to hack the chumby to remove the LCD mute mode, or power it via the external power connector with your own battery pack (9V to 12V).

Like Duane mentioned, this first alpha version of hardware, as with the chumby use case (we think), is intended to be plugged in via wallwart. We didn't do any major power reduction on the board since it wasn't designed to be a battery-powered device. But, that might change if there is significant desire and usage around a portable chumby.

So, if you *do* end up making you chumby portable, please let us know smile

Joe

Re: Power

guys, if you want something portable, buy a pda. chumby doesnt have that much processing power.

need upload space for the forums or a chumby blog? right here then
http://www.nophus.com/useru
username is chumby
password is chumby

22 (edited by jimmypopali 2006-08-29 20:52:02)

Re: Power

chedabob wrote:

guys, if you want something portable, buy a pda. chumby doesnt have that much processing power.

<Bash> the hardware is yet to be released and people are already biting at the bit to get their hands on one and see what they can tweak out of it, the purpose of this forum isnt to criticize people for having an imagination it is to give people a place to brainstorm and throw ideas back and forth about possible improvements and enhancements and to give the developers a chance to look in on what we (possible/soon to be) consumers are thinking, letting them know what WE want. Chumby is made by hackers, people who had very ideas like the people on this board are having right now, "what-ifs" make the world go round. Some say Neccesity is the mother of invention, then Curiousness is it wide grinned father.</Bash>


Jimmy
Edit: Bleh, stupid spelling

Re: Power

chedabob wrote:

guys, if you want something portable, buy a pda. chumby doesnt have that much processing power.

Why buy a PDA when this thing is as powerful as a PDA? Secondly, PDAs aren't very hackable, they're designed to be closed platforms for the most part, and for most, writing software for them a) isn't fun and b) isn't well supported by the community.

This device is fun, it's hackable and more than anything, it's community-driven. I just believe I shouldn't limit its lifespan to being a cute $150 alarm clock, when it's got so much more potential, especially when it gets up and moves with me.

Re: Power

^^

no offense, but what planet are you on? No way is the chumby as powerful as a PDA. ive seen them with 400mhz processors and stuff.

need upload space for the forums or a chumby blog? right here then
http://www.nophus.com/useru
username is chumby
password is chumby

Re: Power

My ideal chumby would look like a sonos cr100 (maybe a bigger screen and less buttons) and have its battery life but still have the chumby price of $150.  big_smile