what is a voltage divider?
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Thanks for the help so far..but I have to ask what is a voltage divider? I
need one for 0 - 300 volts DC. Is this something I have to build or buy?
I am new to all this..but learning fast
Thanks
Jason
need one for 0 - 300 volts DC. Is this something I have to build or buy?
I am new to all this..but learning fast
Thanks
Jason
Comments
"voltage divider" and you will have no problem finding the voltage divider
theory, circuit and appropriate formulas. IF your still having problems post
your calculated values on the list and somone can tell you if you have chosen
correctly.
Good Luck
-=Randy Knutson
miller wrote:
Thanks for the help so far..but I have to ask what is a voltage divider? I
need one for 0 - 300 volts DC. Is this something I have to build or buy?
I am new to all this..but learning fast
Thanks
Jason
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[noparse][[/noparse]Non-text portions of this message have been removed]
lots of basic circuits including voltage dividers.
Al Williams
AWC
* 8 channels of PWM
http://www.al-williams.com/awce/pak5.htm
>
Original Message
> From: miller [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=bLqkvqNrdrGucG_M0J0kLwhA1CUpMLqYlzlUA3Pmqe1ffMeGRZ7HiLdCt2jYtOq5wWYExappLDGxZUKP3p-Uwew]miller12@r...[/url
> Sent: Wednesday, October 09, 2002 12:08 AM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] what is a voltage divider?
>
>
>
> Thanks for the help so far..but I have to ask what is a
> voltage divider? I need one for 0 - 300 volts DC. Is this
> something I have to build or buy? I am new to all this..but
> learning fast
>
> Thanks
> Jason
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the
> Subject and Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
>
>
>
output will vary depending on the varying load that is being pulled from it.
In other words..if your circuit turns a device on and off, the voltage from
your voltage divider will be different when the device is on than when the
device is off. You will have to calculate worst case loading of your voltage
divider.
[noparse][[/noparse]Non-text portions of this message have been removed]
Voltage dividers were invented by Parallax to market stamps. I know I
know, sounds far fetched right? Well thats what they WANT you to
think! Let me tell you a story...
I had some (assumed) faulty modulating motors (Honeywell) that I
wanted to test out on the bench. Not having a handy DDC hookup and
monitor anywhere near where I wanted to work, I decided to rig up a
pair of transformers (+12vdc signal, 24vac motor). Slapped the two
transformers into a nice box, bought a pot and rigged it up to
control the 12vdc. Nice red glow from the pot. Hmmm, thinks I. I
think I've forgotten how to do this. Off to radio shack I go and grab
another pot. I check the net and find a diagram - DOH, forgot the
load resistor so I was roasting the pot when there was no load on the
wiper.
After getting it all working and making it look all cool with a nice
box, I decided to get fancy and throw a dc voltmeter into the lid.
Off to Active components I went. They have nothing along those lines.
I asked about an LCD display and he pointed out some LCDs but said
I'd have to drive it myself. He pointed at the stamp display and I
was instantly addicted. IT WAS A CONSPIRACY!
Just say no to voltage dividers!
>Lies! Lies I tell ya!
>
>Voltage dividers were invented by Parallax to market stamps. I know I
>know, sounds far fetched right? Well thats what they WANT you to
>think! Let me tell you a story...
>
>I had some (assumed) faulty modulating motors (Honeywell) that I
>wanted to test out on the bench. Not having a handy DDC hookup and
>monitor anywhere near where I wanted to work, I decided to rig up a
>pair of transformers (+12vdc signal, 24vac motor). Slapped the two
>transformers into a nice box, bought a pot and rigged it up to
>control the 12vdc. Nice red glow from the pot. Hmmm, thinks I. I
>think I've forgotten how to do this. Off to radio shack I go and grab
>another pot. I check the net and find a diagram - DOH, forgot the
>load resistor so I was roasting the pot when there was no load on the
>wiper.
>
>After getting it all working and making it look all cool with a nice
>box, I decided to get fancy and throw a dc voltmeter into the lid.
>Off to Active components I went. They have nothing along those lines.
>I asked about an LCD display and he pointed out some LCDs but said
>I'd have to drive it myself. He pointed at the stamp display and I
>was instantly addicted. IT WAS A CONSPIRACY!
>
>Just say no to voltage dividers!
Great story... I'm still chuckling. The "trick" to voltage dividers is not
only in the RATIO of the values chosen, but also in the ACTUAL
values. Let's assume a 50-volt source that we want to measure using a
device that wants to see 5 volts maximum. We COULD make a divider
consisting of 1/4 watt resistors with values of 1 ohm and 9 ohms. That
divides the voltage 1:10, but look, a 10 ohm load with 50 volts across it
will allow 5 amps to flow. That's a not so cool 250 watts (man that seems
awful high, but I double checked my math) that will blow the divider
network. Maybe we should try 1K and 9K resistors. That's a more
manageable 1/4 watt of dissipation, but since we don't want to run the
resistors at 100% of the dissipation rating, let's at least double the
resistance once more. I'd go 5 times more, maybe 10 times. Of course the
smaller resistor is probably a pot and has a max resistance 50% or so over
the nominal value so it can be adjusted for calibration... unless you can
get precision resistors with the exact needed values. Either way, taking
power dissipation into consideration, voltage dividers work just fine....
.... unless, in the example above, the measurement device draws enough
current to upset the division of voltage across the divider. In that case
we need a better measuring device, or else we have to lower the resistance
of the divider and up the power rating of the resistors, assuming the
source will tolerate this added load. Typically measuring devices with a
very high impedance are readily available and the power draw by the
measuring device can be ignored.
Jim H
http://www.wd5gnr.com/basiccir.htm
Al Williams
AWC
* NEW: PAK-VIa - Read PS/2 keyboards or mice -- double the buffer, lower
current consumption.
http://www.al-williams.com/awce/pak6.htm
>
Original Message
> From: miller [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=-No75MiRlDcC8i8sTB_DLIvMo-ltLXavv3Z0CM_KM3ximRHp0tblIxCvzRTR1uGSNp6rChtVCbVoY3yyc_iL5A]miller12@r...[/url
> Sent: Wednesday, October 09, 2002 12:08 AM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] what is a voltage divider?
>
>
>
> Thanks for the help so far..but I have to ask what is a
> voltage divider? I need one for 0 - 300 volts DC. Is this
> something I have to build or buy? I am new to all this..but
> learning fast
>
> Thanks
> Jason
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the
> Subject and Body of the message will be ignored.
>
>
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> http://docs.yahoo.com/info/terms/
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>
>
On Mon, 2002-10-28 at 16:19, Al Williams wrote:
> In addition to the other answers, you might enjoy reading:
> http://www.wd5gnr.com/basiccir.htm
>
> Al Williams
playing with voltages (0 to 300 vdc) which can kill you! Please get a copy
of any ARRL handbook and at least learn some basics before you have a lethal
accident!
Jim
Original Message
From: Al Williams [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=kfO_P_WQU-iyNkE9H7_yqJadrnLGqUjH6AVzDUw3M0aqEsNDCPMtKh2P0dhSUKqXQlocj4yIXay0TkTY]alw@a...[/url
Sent: Monday, October 28, 2002 4:20 PM
To: basicstamps@yahoogroups.com
Subject: RE: [noparse][[/noparse]basicstamps] what is a voltage divider?
In addition to the other answers, you might enjoy reading:
http://www.wd5gnr.com/basiccir.htm
Al Williams
AWC
* NEW: PAK-VIa - Read PS/2 keyboards or mice -- double the buffer, lower
current consumption.
http://www.al-williams.com/awce/pak6.htm
>
Original Message
> From: miller [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=d6fh9nFoYhFrCqSf6jHCKPeOTPo4slwT5FLsJTryEWdrGnQuDsNQUZpeSIo5AhCR8yXbBsr40qdXR8p9Xrw]miller12@r...[/url
> Sent: Wednesday, October 09, 2002 12:08 AM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] what is a voltage divider?
>
>
>
> Thanks for the help so far..but I have to ask what is a
> voltage divider? I need one for 0 - 300 volts DC. Is this
> something I have to build or buy? I am new to all this..but
> learning fast
>
> Thanks
> Jason
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the
> Subject and Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
>
>
>
To UNSUBSCRIBE, just send mail to:
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of 10:1 up to 10000:1. So at 1:100 a 300VDC would read 3VDC. Just
send this into a A2D chip then to the stamp. The ones we use cost
about $9. Your mileage may vary. Did I mention a tolerance of .1% to
.05%?
www.caddock.com
Hope this helps
Paul
> Date: Mon, 28 Oct 2002 15:19:59 -0600
> From: "Al Williams" <alw@a...>
>Subject: RE: what is a voltage divider?
>
>In addition to the other answers, you might enjoy reading:
>http://www.wd5gnr.com/basiccir.htm
>
>Al Williams
>AWC
>* NEW: PAK-VIa - Read PS/2 keyboards or mice -- double the buffer,
>lower
>current consumption.
>http://www.al-williams.com/awce/pak6.htm
>
>
Original Message
> From: miller [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=YmZFdIVxC2uv9FSBQGyiMsrVJxnj-31D-KoR_zC3KzC5K8Xm9k1fxLtaFB0FZS2KI89VWE4Qn72xubUyOUg]miller12@r...[/url
> Sent: Wednesday, October 09, 2002 12:08 AM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] what is a voltage divider?
>
>
>
> Thanks for the help so far..but I have to ask what is a
> voltage divider? I need one for 0 - 300 volts DC. Is this
> something I have to build or buy? I am new to all this..but
> learning fast
>
> Thanks
> Jason
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the
> Subject and Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
>
>
>
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