Buck/Boost regulator for propeller

hinv

Hi,

I have spend a few hours no trying to figure out why my PELab propeller program wasn't working correctly until I got out my multimeter and noticed the voltage sags when the LEDs.
The problem is the 9V battery goes dead pretty quick. Can someone recommend a Buck/Boost regulator I could use for this that is quite a bit more battery efficient?

Thanks,
Doug

mctrivia

first of all don't use a 9v. they are not very powerful. a couple aa batteries are pretty good.

my propmods use a TPS63001DRCR to allow for 1.8V to 5.5V input with 3.3V out.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
propmod_us are now in stock. propmod_1x1 arrive on 26th. Only $30

Need to upload large images or movies for use in the forum. you can do so at uploader.propmodule.com for free.

Mike Green

The problem is that a 9V battery has a very low capacity and LEDs are fairly power hungry. Do a web search for Eveready Energizer 9V Alkaline and you'll find a typical datasheet for a 9V alkaline battery. The datasheet has a variety of graphs that show the battery life for various loads. The Propeller itself draws different amounts of power depending on how many cogs are active and what the system clock speed is set to. The Propeller datasheet has several graphs that give this information.

A buck-boost regulator will be of limited help. You'd be better off using 5 AA NiMH cells with a typical capacity of 2300mAh or a 4 AA alkaline disposable cells. RadioShack has a 4 x AA battery holder and a 1 x AA battery holder that you can wire in series

Dr_Acula

I like the LM2575 'simple switcher' One 5 pin reg. One switching reg diode and one inductor. Total cost can end up less than a standard reg plus heatsink. For the prop you would need the 3V version. That is a little harder to find than the 5V one, but there are variable ones and you could set the volts with a trimpot and then just leave it. The inductor is a bit hard to get - it needs to handle an amp so the little tiny inductors used for RF filters are too small. I picked up a whole lot once for $2 each. There are prebuilt modules on ebay and there are modules from places like futurlec for $6 or so. If you find a source, but quite a few as they come in handy. I've got a drawer full of the inductors, regs and diodes. Once you have the parts, building one is quick - just a matter of soldering three components. Plus the caps - but a standard reg design has those anyway.

Phil Pilgrim (PhiPi)

Another alternative offering high capacity is a CR123A lithium 3V primary cell. Out of the package, they test at 3.25V and don't sag below 3V until the very end of their life.

-Phil

BADHABIT

or a 9v lithium

Philldapill

I think Phil's point was that the CR123A could run the propeller directly - no regulator needed for the life of the battery. A 9V battery would need a regulator, thus wasting power...

hinv

Wow, thanks guys. You are a big help.

I don't know if I need 5 V yet or not because I am only one Lab 5.
I also have the PropStick USB version of the PEKit. I think this was a mistake because it has a 3.3V regulator on it, and it doesn't have a sticker showing the pinouts right on the chip like the original version has.
I may just order the parts to convert it back to a regular PEKit and go with a different regulator. In the short term, I will look into a LM2575, because I believe I may have some on some scrap boards, but for 3.3v only projects the TPS63001DRCR sound's like a better deal.

heater

This is something that has puzzled me for a while.

I'd like to be able to run my home made Prop Demo Board style board from 4 times Ni-MH AA size rated at 2700mAh.

Why: Because I happen the charger and 4 such cells, they are cheap and easy to come by.

Problem is of course that the output starts at 5.6volts full charge and soon drops below that at which I can get the regulated 5v. I guess it would help a little to have a LDO regulator instead of what ever junk I have in there now.

Using 5 cells is a no no. Just seems very clunky and inelegant. Charging all 4 cells at a time is so convenient.

What I'd like is a boost/buck regulator that will regulate down to 5v in the fully charged state and boost up to 5v as cells droop down to say 4v. Thus making maximum use of the charge.

Is there such a boos/buck regulator that will achieve this? Hopefully something simple enough to assemble at home.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
For me, the past is not over yet.

heater

Of course what would be really cool is if some electronics guru could suggest a circuit with a handful of capacitors resistors, an inductor and a transistor or two such that the Prop itself could boost and buck to 5V for external circuitry. After all we can do PWM and ADC so why not?

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
For me, the past is not over yet.

heater

Perhaps this is the answer to my question: embeddedmicro.com/index.php/prototyping/power-management/to-220-sized-5v-3-3v-charge-pump.html

EDIT: Ah no. The 25 dollar freight is a no go.

Any other options/suggestions ?

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
For me, the past is not over yet.

Post Edited (heater) : 5/24/2009 11:58:33 AM GMT

virtuPIC

Other suggestions? What about that: Designer's Notebook?

If you want even less hardware there is at least a circuit for AVR. It uses the very nice concept of replacing hardware by software. It implements the controller of the converter in a small program. To start the device push a switch to give the converter a kick for the first pulse. Unfortunately, this probably won't suffice to load the propeller RAM from EEPROM or via serial.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Airspace V - international hangar flying!
www.airspace-v.com/ggadgets for tools & toys

Fred Hawkins

heater said...


What I'd like is a boost/buck regulator that will regulate down to 5v in the fully charged state and boost up to 5v as cells droop down to say 4v. Thus making maximum use of the charge.

Is there such a boos/buck regulator that will achieve this? Hopefully something simple enough to assemble at home.

TI's tps63002 is the 5.0 v flavor. 10 pin qfn package which may or not be simple enough.

mctrivia

the tps63002 max input voltage is 5.5V the 0.1V difference may or may not be a problem. either way if you need a pcb the back half of my propmod has the layout for that ic and suporting caps and resisters and even space for a small fuse. Very tiny though. The board area needed for the power upply is 0.4"x0.8"

If just ordering a pcb i can probably get in a regular envelope and ship for $1 or so.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
propmod_us are now in stock. propmod_1x1 arrive on 26th. Only $30

Need to upload large images or movies for use in the forum. you can do so at uploader.propmodule.com for free.

heater

Great. Thanks for the suggestions guys.

virtuPIC: That note book is brilliant. 433V from CMOS inverters, would never have dreamt it. May get my old oscilloscope tube fired up after all! Thanks.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
For me, the past is not over yet.

Mike Green

I think it was Beau that posted a boost regulator using a Prop cog way back when the Prop was relatively new. I don't have a link, but you could browse for it easily enough.

heater

Cheers Mike. I think you mean this booster http://forums.parallax.com/showthread.php?p=597359

Man it's hard work to find anything around here.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
For me, the past is not over yet.

Joel Rosenzweig

I have run into this problem, too.· I wanted to run the Prop and one of the Serial LCD modules with backlight from a 4-cell NiCD pack.· Regulating the voltage to 3.3 volts was no problem, but ensuring the·voltage to the display never dipped below 5.0v was a problem that I never quite solved elegantly.·

I found this device which looks like it would work very well:

http://www.dimensionengineering.com/AnyVoltMicro.htm

Maybe it will work for you?

Joel-


▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
I saved Earth from an Alien Attack.· Can you?

·

mctrivia

On phone so I can't check but is that not buck only?

63002 is fairly easy to use to get 5v out.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
propmod_us are now in stock. propmod_1x1 arrive on 26th. Only $30

Need to upload large images or movies for use in the forum. you can do so at uploader.propmodule.com for free.

Rayman

Just my 2 cents... I'm doing a design right now with the MAX756. It comes in 8-pin DIP and can generate either 5 or 3.3 V. It's a very simple way to go, and could probably even work on a breadboard...

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm

mctrivia

the max756 is boost only. which is not necessarily a problem. Using a switching supply on a breadboard is not a good idea.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
propmod_us are now in stock. propmod_1x1 arrive on 26th. Only $30

Need to upload large images or movies for use in the forum. you can do so at uploader.propmodule.com for free.

Toby Seckshund

One thing to watch with regulators, when they get close to their dropout is that they can become very power hungry themselves. Their normal quiesent current shoots up and will drain that battery, they always seem to want a couple of volts headroom to run properly, desite published dropout figures. Just what you don't want because of heat and battery usage.

I keep meaning to try using one li cell to see if 4.0V to 4.2V is really that evil. Now the price has dropped, here in UK, I might give it a trial

hinv

@PhiPi: Thanks for the CR123A tip. I hadn't considered it until I just recently found a rechargeable one on ebay. The thought of throwing away batteries seems so wasteful. Where would I find a socket for a CR123A?

Thanks,
Doug

Toby Seckshund

I have just looked at that AVR cct, I love the fact that it requires a "starting handle". On a prop would you require goggles and have to shout "CONTACT!!!"