Greetings All
Can I make voltage multipliers from several ULN2003A Darlington Array IC
chips?
I'm trying to increase the voltage out my National Instruments usb-6008. I
have several ULN2003A DARLINGTON ARRAYS I was wondering if I could use
these as VOLTAGE MULTIPLIERS. I have 3v coming out my usb6008 and I'm
trying to get to about 16v or would I need to use a different chip.
Anyone have any examples with this chip? I'm using Multisim 9 to test
different configurations out.
Tia Sal2
Hi, Tia Sal. Your idea won't work. The input to a voltage multiplier
needs to source *and* sink current -- the ULN2003 only sinks. Not only
that, but the darlington output means the output voltage never goes
below 1V, no matter how little current it's sinking. Once you subtract
another diode drop, you'll need a lot of stages to get to 16V.
Before anything else, though, it's odd you say you've got 3V. The spec
sheet says you get 5V at 200mA max at the output I/O connector. This
comes direct from the USB, I think.
Now if you were on a desert island and a ULN2003 was all you had, or if
an evil genie or professor were holding your feet to the fire, you
might be able to get away with switching an inductor on and off without
using the ULN2003 internal diode, and then use a diode, cap and zener
to give you a very low current 16V supply like this (view in fixed font
or M$ Notepad):
|
| VCC
| +
| |
| C|
| C| L
| 1/7 C|
| ULN2003 |
| |\ |1N4148
| -| >O---o->|-o----o----o
| |/ +| |
| 47uF --- /-/1N4745A
| 35V --- ^ Vz=16V
| | |
| === ===
| GND GND
|
(created by AACircuit v1.28.6 beta 04/19/05
www.tech-chat.de)
You need a good value inductor to give you the inductive kick, and it
should have a DC resistance of at least 20 ohms (4V / .2A). If that's
a problem, you might want to play with the duty cycle, and have a local
supply for the inductor separated by a 20 ohm resistor and, say, a
220uF cap like this:
|
| ___
| VCC+o-|___|-o------.
| 33 ohm +| |
| 220uF--- |
| 16V --- |
| | C|
| GND C| L
| 1/7 C|
| ULN2003 |
| |\ |1N4148
| -| >O---o->|-o----o----o
| |/ +| |
| 47uF --- /-/1N4745A
| 35V --- ^ Vz=16V
| | |
| === ===
| GND GND
|
(created by AACircuit v1.28.6 beta 04/19/05
www.tech-chat.de)
This will allow you to choose a DC coil resistance that keeps current
as less than the max for the ULN2003. Again, you'll have to leave pin
16 open (which might mess up your other plans with the ULN2003, if
you're switching anything else inductive).
If this is a real-world project, this is a little cheesy -- you
definitely should use a DC-to-DC converter instead of this unless you
only need a couple of mA and good regulation isn't a problem.
Don't worry about having spare stuff left over when you're done with a
project. It's not like the broccoli your mom served you. You should
be crafty, but you don't have to use 'em all.
And make sure to read the data sheets, sir. They're not printed
because the manufacturers hate trees. And you can always get the .pdf
file if you're concerned about the clutter of paper, or have
environmental reservations.
Go Aztecs!
Chris