Looking for a way to remotely measre 12v and 24v with a sing

> It's hard to beat the simplicity of two resistors.  :^)

Yeah. But my relay gizmo is way cooler.

Cheers

Phil Hobbs

 

On Wednesday, April 8, 2020 at 4:25:09 PM UTC-4, John Larkin wrote:

On Wed, 08 Apr 2020 16:00:32 -0400, Steve <nospam@nowhere.org> wrote:

I have been a lurker in this group for some time. This is a totally
non-political post.

I have a remote controlled gate located around 150' from the house. The gate
runs off 24VDC, and the electronics runs off 12VDC. The 12V is being supplied
by a 24V to 12V switching power supply. Right now, I am getting a solid 12V
(measured) from the power supply.

The 24V power is being fed to the gate by 2 #8 wires from a 24V battery-backup
power supply in the house. The voltage drop on these wires is negligible, and I
am getting a solid 24V (measured) at the gate..

I would like to remotely measure both the 24V and 12V at the gate.

Right now, I have a single free wire going between the gate and the house that I
can use without pulling more cable. The wire is now connected to the 24V supply
at the gate, and a voltmeter in the house, but I would like to monitor both the
24V supply and the 12V supply, and don't want to pull more cable between the
house and gate.

Does anyone know of a simple and cheap way to monitor both voltages using only
the one wire? Ground is available through a number of cables, so, ground
reference is not an issue.

Thanks in advance.

Steve

A resistor and a diode could provide you a source that is 24 volts if
unloaded, and drops to 12 when loaded. On the DVM end, the load could
be a resistor and a pushbutton.

Something fancier could alternate the voltages.

But if the 12 volts looks OK, isn't it very probable that the 24 is OK
too?


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

He can make two over/under '431 comparators confirming say 7.5% supply tolerances signaling the result over the single wire using the 12V wire-AND output to drive a LED or something. Then he has the 12V signal and the 24V source both available for observation by meter if needed, although not necessary unless something breaks.

 

[George Herold]

On Friday, April 10, 2020 at 12:29:23 AM UTC-4, ehsjr wrote:

On 4/9/2020 3:19 PM, Bill Martin wrote:
On 4/9/20 8:30 AM, George Herold wrote:
On Thursday, April 9, 2020 at 6:20:05 AM UTC-4, blo...@columbus.rr.com
wrote:
On Wednesday, April 8, 2020 at 4:25:09 PM UTC-4, John Larkin wrote:
On Wed, 08 Apr 2020 16:00:32 -0400, Steve <nospam@nowhere.org> wrote:

I have been a lurker in this group for some time.  This is a totally
non-political post.

I have a remote controlled gate located around 150' from the
house.  The gate
runs off 24VDC, and the electronics runs off 12VDC.  The 12V is
being supplied
by a 24V to 12V switching power supply.  Right now, I am getting a
solid 12V
(measured) from the power supply.

The 24V power is being fed to the gate by 2 #8 wires from a 24V
battery-backup
power supply in the house.  The voltage drop on these wires is
negligible, and I
am getting a solid 24V (measured) at the gate..

I would like to remotely measure both the 24V and 12V at the gate.

Right now, I have a single free wire going between the gate and the
house that I
can use without pulling more cable.  The wire is now connected to
the 24V supply
at the gate, and a voltmeter in the house, but I would like to
monitor both the
24V supply and the 12V supply, and don't want to pull more cable
between the
house and gate.

Does anyone know of a simple and cheap way to monitor both voltages
using only
the one wire?  Ground is available through a number of cables, so,
ground
reference is not an issue.

Thanks in advance.

Steve

A resistor and a diode could provide you a source that is 24 volts if
unloaded, and drops to 12 when loaded. On the DVM end, the load could
be a resistor and a pushbutton.

Something fancier could alternate the voltages.

But if the 12 volts looks OK, isn't it very probable that the 24 is OK
too?


--

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

Use a resistor divider between 24V and 12V.  You should get 18V.
Send the 18V back to the hose and set up to comparators in your house
to monitor over18V and under 18V

Ahh good. I knew there was at least one difference circuit, but I was
thinking the wrong way.

GH

how would you get >18V for either supply failed? The idea looks
workable, but the compare levels don't look right...
-bill m


OPEN output failure:
If 12V fails you get 24 volts from the divider;
if 24V fails you get 12 volts from the divider;
if both fail you get 0 volts from the divider.

SHORTED output failure:
If 12V shorts you get 12 volts from the divider;
if 24V shorts you get 6 volts from the divider;
if both fail you get 0 volts from the divider.

If both work, you get 18 volts from the divider.

Unspecified failure = unspecified output from divider.

Ed

It's hard to beat the simplicity of two resistors. :^)

GH

 

[George Herold]

On Friday, April 10, 2020 at 11:25:48 AM UTC-4, pcdh...@gmail.com wrote:

It's hard to beat the simplicity of two resistors.  :^)

Yeah. But my relay gizmo is way cooler.

Cheers

Phil Hobbs

Yeah I put that away in the back of my brain, in case someday
I have to sample two time varying signals over one wire.

George H.

 

[Ricky C]

On Friday, April 10, 2020 at 11:08:56 AM UTC-4, George Herold wrote:

On Friday, April 10, 2020 at 12:29:23 AM UTC-4, ehsjr wrote:
On 4/9/2020 3:19 PM, Bill Martin wrote:
On 4/9/20 8:30 AM, George Herold wrote:
On Thursday, April 9, 2020 at 6:20:05 AM UTC-4, blo...@columbus.rr.com
wrote:
On Wednesday, April 8, 2020 at 4:25:09 PM UTC-4, John Larkin wrote:
On Wed, 08 Apr 2020 16:00:32 -0400, Steve <nospam@nowhere.org> wrote:

I have been a lurker in this group for some time.  This is a totally
non-political post.

I have a remote controlled gate located around 150' from the
house.  The gate
runs off 24VDC, and the electronics runs off 12VDC.  The 12V is
being supplied
by a 24V to 12V switching power supply.  Right now, I am getting a
solid 12V
(measured) from the power supply.

The 24V power is being fed to the gate by 2 #8 wires from a 24V
battery-backup
power supply in the house.  The voltage drop on these wires is
negligible, and I
am getting a solid 24V (measured) at the gate..

I would like to remotely measure both the 24V and 12V at the gate..

Right now, I have a single free wire going between the gate and the
house that I
can use without pulling more cable.  The wire is now connected to
the 24V supply
at the gate, and a voltmeter in the house, but I would like to
monitor both the
24V supply and the 12V supply, and don't want to pull more cable
between the
house and gate.

Does anyone know of a simple and cheap way to monitor both voltages
using only
the one wire?  Ground is available through a number of cables, so,
ground
reference is not an issue.

Thanks in advance.

Steve

A resistor and a diode could provide you a source that is 24 volts if
unloaded, and drops to 12 when loaded. On the DVM end, the load could
be a resistor and a pushbutton.

Something fancier could alternate the voltages.

But if the 12 volts looks OK, isn't it very probable that the 24 is OK
too?


--

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

Use a resistor divider between 24V and 12V.  You should get 18V.
Send the 18V back to the hose and set up to comparators in your house
to monitor over18V and under 18V

Ahh good. I knew there was at least one difference circuit, but I was
thinking the wrong way.

GH

how would you get >18V for either supply failed? The idea looks
workable, but the compare levels don't look right...
-bill m


OPEN output failure:
If 12V fails you get 24 volts from the divider;
if 24V fails you get 12 volts from the divider;
if both fail you get 0 volts from the divider.

SHORTED output failure:
If 12V shorts you get 12 volts from the divider;
if 24V shorts you get 6 volts from the divider;
if both fail you get 0 volts from the divider.

If both work, you get 18 volts from the divider.

Unspecified failure = unspecified output from divider.

Ed

It's hard to beat the simplicity of two resistors. :^)

GH

But it's only a pass/fail indicator and you can get that by seeing if the gate works.

--

Rick C.

+ Get 1,000 miles of free Supercharging
+ Tesla referral code - https://ts.la/richard11209

 

[Ricky C]

On Friday, April 10, 2020 at 11:25:48 AM UTC-4, pcdh...@gmail.com wrote:

It's hard to beat the simplicity of two resistors.  :^)

Yeah. But my relay gizmo is way cooler.

Cheers

Phil Hobbs

Seems to me the oscillator is a pretty good idea. I'm not sure how the first poster was trying to use it, but using a ~50/50 duty cycle running between the two power supplies slowly enough you can just connect a meter to the single wire and read the two voltages in just three or four seconds. No conversions or translations or diode adjustments needed.

I don't think a 555 timer could be used though. None of them I've seen are rated for 24 volts. A simple 2 transistor astable oscilator would work fine.

--

Rick C.

-- Get 1,000 miles of free Supercharging
-- Tesla referral code - https://ts.la/richard11209

 

[ehsjr]

On 4/10/2020 11:25 AM, pcdhobbs@gmail.com wrote:

It's hard to beat the simplicity of two resistors.  :^)

Yeah. But my relay gizmo is way cooler.

Yup. And better, too, because then he can actually measure
the voltages.

Ed

Cheers

Phil Hobbs