I have a computer connected to my Arduino on a robot platform. The Arduino will get 5 volts from a USB connection, but the computer takes 19 vdc at 40 watts. I only have two 12-volt car batteries, for a total of 24 volts. The batteries are already connected in series, so I can't step up the voltage from one battery, I can only reduce the voltage from the pair.
Does anyone have an easy way to reduce this voltage from 24 volts to 19 volts at 40 watts?
but the computer takes 19 vdc
19V is an odd value. Is that the spec, or did you measure it?
Look for a DC-DC converter or an adjustable switching voltage regulator chip. (A linear regulator is unlikely to handle the power.)
at 40 watts
A DC-DC converter is likely to have a wattage rating. Voltage regulators are generally rated by voltage and current. (Power = Voltage x Current, so you'll need a little more than 2 Amps.)
19 V is a fairly standard laptop supply voltage, isn't it?
Voltage divider using some high load resistors.
Johnny010:
Voltage divider using some high load resistors.
No.
Just. . . no.
Some sort of UBEC?
Johnny010:
Voltage divider using some high load resistors.
a thousand times no...
Johnny010:
Some sort of UBEC?
What's a ubec?
You need to drop 5 volts while supplying approximately two amps. Since the supply is a battery, do you expect the supply voltage to drop below say 21 or 22 volts? If so, you'll want a regulator that can boost the voltage so that it can supply 19 volts even when the battery voltage drops below 21 volts or less. Something like this module:http://www.ebay.com/itm/150W-DC-DC-Boost-Converter-10-32V-12-35V-6A-Step-Up-Charger-Power-Module-/310523503559?pt=LH_DefaultDomain_0&hash=item484ca4a3c7
If you know the supply voltage from the battery will never drop below 21-22 volts, you can use a buck mode module (it can not raise the output voltage above the input voltage, unlike like a boost mode module). While it has a constant current mode that you would not use, this would be a good choice for a buck mode module: http://www.ebay.com/itm/5A-Lithium-Charger-CV-CC-buck-Step-down-Power-Supply-Module-LED-Driver-New-/201114996886?pt=LH_DefaultDomain_0&hash=item2ed3635096
Good luck with the project!
20V is the output of the brick for may laptop.
You may have to get an inverter to go from 24V to 120V, and let the laptop power brick get you down to 19V.
What happened to the laptop battery.
I think the inverter is the best option suggested.
AWOL:
19 V is a fairly standard laptop supply voltage, isn't it?
Yes it is. My Acer monitor also has a 19v switching power supply.
Alligator:
I have a computer connected to my Arduino on a robot platform. The Arduino will get 5 volts from a USB connection, but the computer takes 19 vdc at 40 watts. I only have two 12-volt car batteries, for a total of 24 volts. The batteries are already connected in series, so I can't step up the voltage from one battery, I can only reduce the voltage from the pair.Does anyone have an easy way to reduce this voltage from 24 volts to 19 volts at 40 watts?
24 volts to 19 volts at 40 watts means you have to drop 5 volts at about 2.1 amperes. Using a simple linear regulator, you would have to dissipate about 10 watts of heat. Not at all too bad.
I would use an LM350 and program it with a 150 ohm / 2200 ohm set.
Put it on a decent heatsink and you're all set.
What's a ubec?
UBEC = Universal Battery Eliminator Circuit.
It's a module used to drop "high" voltage (20 to 30) down to 6 volts for radio control servos and radios.
It's completely useless for the OP's requirements, which makes me wonder why "Voltage Divider Johnny" even mentioned it (or for that matter why he mentioned resistors).
You can easily get devices to drive a laptop from a 12v supply so they can be powered from (for example) a car. I wonder if there are similar devices that work from 24v for use in trucks?
...R
This high power Buck Converter works well for powering 19V laptops from 24V supply.
Not to expensive at $7.99 w/free shipping.
Voltage divider using some high load resistors.
(¡Gensanta!). 40 w?. Voltage divider?.