Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: blackbeard on September 10, 2010, 06:39:35 AM

Title: voltage doublers for tiny robots
Post by: blackbeard on September 10, 2010, 06:39:35 AM
hey guys. i've been researching voltage doublers which i would like to use with a small lithium ion battery running at 3.7v in order to power 2 micro servos and a atmel microcontroler. what i was wondering is if anyone has had any experience with these and whether or not they draw too much power to be worth using in a small bot.
Title: Re: voltage doublers for tiny robots
Post by: voyager2 on September 10, 2010, 07:27:07 AM
http://en.wikipedia.org/wiki/Voltage_doubler (http://en.wikipedia.org/wiki/Voltage_doubler)
Google also came up with some ineresting results
http://www.google.com.au/#hl=en&source=hp&q=voltage+doubler&aq=0&aqi=g10&aql=&oq=Voltage+Doub&gs_rfai=&fp=9917c9767e3ed06a (http://www.google.com.au/#hl=en&source=hp&q=voltage+doubler&aq=0&aqi=g10&aql=&oq=Voltage+Doub&gs_rfai=&fp=9917c9767e3ed06a)

It's good to remember, that you never get anything free in electronics, while the Voltage is doubled, the available current is halved (it does depend on your circuit)
Title: Re: voltage doublers for tiny robots
Post by: madsci1016 on September 10, 2010, 07:41:43 AM
hey guys. i've been researching voltage doublers which i would like to use with a small lithium ion battery running at 3.7v in order to power 2 micro servos and a atmel microcontroler. what i was wondering is if anyone has had any experience with these and whether or not they draw too much power to be worth using in a small bot.

How much room/money do you have to work with?

I like the Dimension Engineering AnyVolt Micro (http://www.dimensionengineering.com/AnyVoltMicro.htm), but it's $20 and only runs 500mA. There are cheaper similar products, but DE products are higher quality; better power quality.

Or you could build your own, with a Boost converter IC, and inductor and some capacitors. 
Title: Re: voltage doublers for tiny robots
Post by: blackbeard on September 10, 2010, 08:34:27 AM
http://en.wikipedia.org/wiki/Voltage_doubler (http://en.wikipedia.org/wiki/Voltage_doubler)
Google also came up with some ineresting results
http://www.google.com.au/#hl=en&source=hp&q=voltage+doubler&aq=0&aqi=g10&aql=&oq=Voltage+Doub&gs_rfai=&fp=9917c9767e3ed06a (http://www.google.com.au/#hl=en&source=hp&q=voltage+doubler&aq=0&aqi=g10&aql=&oq=Voltage+Doub&gs_rfai=&fp=9917c9767e3ed06a)

It's good to remember, that you never get anything free in electronics, while the Voltage is doubled, the available current is halved (it does depend on your circuit)

yep i've google'd many schematics but i was wondering if people had first hand accounts.
Title: Re: voltage doublers for tiny robots
Post by: amando96 on September 10, 2010, 10:02:26 AM
I'd get those 3.7v down to 3.3v and use it like that, 5v is dying, though you'd need an extra battery for your servos...

Pololu has a few adjustable DC boost regulators, in the $10s, be sure to check the current they can handle... servos pull more than one might think, and cheap DC boosts can handle 200-500 mA
Title: Re: voltage doublers for tiny robots
Post by: Razor Concepts on September 10, 2010, 10:06:13 AM
Some ultramicro servos are designed to run on 1s lipo. AVRs also can run at the low voltages
Title: Re: voltage doublers for tiny robots
Post by: amando96 on September 10, 2010, 10:14:05 AM
The atmegaXXXP will run with 3.3v, if it doesn't have the P it needs 4.5v to 5.5v to operate.
Title: Re: voltage doublers for tiny robots
Post by: waltr on September 10, 2010, 10:38:35 AM
In general: simple voltage doubles work well for low current outputs. As the current demand increases it gets harder to supply.

How much current does the servo draw? This is where you need to start for a design.

For more than a few 10's of mA it would be better to use one of the Boost convert chips. Linear Tech and others make some nice easy to use chips that can be set to almost any output voltage desired.
Title: Re: voltage doublers for tiny robots
Post by: Asellith on September 10, 2010, 02:55:50 PM
Admin has some posts someplace on here about servo currents. He did a lot of testing/research for his fish project a while back. If you can find those they might be a good place to start