1-Wire ADC...

[Ricketty C]

On Monday, July 20, 2020 at 2:22:16 PM UTC-4, David Lesher wrote:

Was looking for a way to monitor a number of 12V deep cycle L-A batteries.
Since we have an installed 1-Wire network, it would be nice if we could
just add on to that.

But I notice a dearth of 1-Wire ADC\'s.
Any idea why?

Any digital device can be a 1-wire device. I would just program up a cheap MCU with a built in ADC to be controlled over 1-wire. It just takes a resistor and a cap to power it. No?

--

Rick C.

- Get 1,000 miles of free Supercharging
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[Bill Sloman]

On Tuesday, July 21, 2020 at 11:22:51 AM UTC+10, George Herold wrote:

On Monday, July 20, 2020 at 8:42:33 PM UTC-4, David Lesher wrote:
boB <boB@K7IQ.com> writes:

But I notice a dearth of 1-Wire ADC\'s.
Any idea why?


Not sure why there aren\'t any around ?

But we/I made our own for a battery shunt, in the negative lead A/D
monitor. Single wire is the power and two way data but only about 10
conversions per second in this case. The shunt is the second wire.

Used a 35 cent micro and I2C A/D. I don\'t see why you couldn\'t
address more than one of these on a single wire.

I suppose it all depends on how fast you need the data to be

Every few minutes will do.....

I know nothing of ADCs, but isn\'t this successive approximation?
maybe you have the wrong search term?

At that sort of sampling speed it\'s almost always sigma-delta - pulse-width modulation of the probe voltage to match the voltage being measured. Typically good to about 20-bit accuracy if the software keeps on trying for long enough.

--
Bill Sloman, Sydney

 

[Bill Sloman]

On Tuesday, July 21, 2020 at 11:22:51 AM UTC+10, George Herold wrote:

On Monday, July 20, 2020 at 8:42:33 PM UTC-4, David Lesher wrote:
boB <boB@K7IQ.com> writes:

But I notice a dearth of 1-Wire ADC\'s.
Any idea why?


Not sure why there aren\'t any around ?

But we/I made our own for a battery shunt, in the negative lead A/D
monitor. Single wire is the power and two way data but only about 10
conversions per second in this case. The shunt is the second wire.

Used a 35 cent micro and I2C A/D. I don\'t see why you couldn\'t
address more than one of these on a single wire.

I suppose it all depends on how fast you need the data to be

Every few minutes will do.....

I know nothing of ADCs, but isn\'t this successive approximation?
maybe you have the wrong search term?

At that sort of sampling speed it\'s almost always sigma-delta - pulse-width modulation of the probe voltage to match the voltage being measured. Typically good to about 20-bit accuracy if the software keeps on trying for long enough.

--
Bill Sloman, Sydney

 

[Bill Sloman]

On Tuesday, July 21, 2020 at 11:22:51 AM UTC+10, George Herold wrote:

On Monday, July 20, 2020 at 8:42:33 PM UTC-4, David Lesher wrote:
boB <boB@K7IQ.com> writes:

But I notice a dearth of 1-Wire ADC\'s.
Any idea why?


Not sure why there aren\'t any around ?

But we/I made our own for a battery shunt, in the negative lead A/D
monitor. Single wire is the power and two way data but only about 10
conversions per second in this case. The shunt is the second wire.

Used a 35 cent micro and I2C A/D. I don\'t see why you couldn\'t
address more than one of these on a single wire.

I suppose it all depends on how fast you need the data to be

Every few minutes will do.....

I know nothing of ADCs, but isn\'t this successive approximation?
maybe you have the wrong search term?

At that sort of sampling speed it\'s almost always sigma-delta - pulse-width modulation of the probe voltage to match the voltage being measured. Typically good to about 20-bit accuracy if the software keeps on trying for long enough.

--
Bill Sloman, Sydney

 

[boB]

On Tue, 21 Jul 2020 09:51:29 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Tue, 21 Jul 2020 00:42:29 +0000 (UTC), David Lesher
wb8foz@panix.com> wrote:

boB <boB@K7IQ.com> writes:

But I notice a dearth of 1-Wire ADC\'s.
Any idea why?


Not sure why there aren\'t any around ?

But we/I made our own for a battery shunt, in the negative lead A/D
monitor. Single wire is the power and two way data but only about 10
conversions per second in this case. The shunt is the second wire.

Used a 35 cent micro and I2C A/D. I don\'t see why you couldn\'t
address more than one of these on a single wire.

I suppose it all depends on how fast you need the data to be

Every few minutes will do.....

Common grounds are another obstacle. Hard to measure batteries in series...

I once invented a leapfrog matrix of current-limited SSRs to check a
series string of batteries. Odd/even nodes are switched to opposite
sides of a floating, bipolar ADC.

A couple more SSRs could make a flying-capacitor isolator.

Kind of like a Lithium battery BMS sounds like.

 

[boB]

On Tue, 21 Jul 2020 09:51:29 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Tue, 21 Jul 2020 00:42:29 +0000 (UTC), David Lesher
wb8foz@panix.com> wrote:

boB <boB@K7IQ.com> writes:

But I notice a dearth of 1-Wire ADC\'s.
Any idea why?


Not sure why there aren\'t any around ?

But we/I made our own for a battery shunt, in the negative lead A/D
monitor. Single wire is the power and two way data but only about 10
conversions per second in this case. The shunt is the second wire.

Used a 35 cent micro and I2C A/D. I don\'t see why you couldn\'t
address more than one of these on a single wire.

I suppose it all depends on how fast you need the data to be

Every few minutes will do.....

Common grounds are another obstacle. Hard to measure batteries in series...

I once invented a leapfrog matrix of current-limited SSRs to check a
series string of batteries. Odd/even nodes are switched to opposite
sides of a floating, bipolar ADC.

A couple more SSRs could make a flying-capacitor isolator.

Kind of like a Lithium battery BMS sounds like.

 

[server]

On Tue, 21 Jul 2020 12:31:05 -0700 (PDT), Ricketty C
<gnuarm.deletethisbit@gmail.com> wrote:

On Tuesday, July 21, 2020 at 11:25:57 AM UTC-4, upsid...@downunder.com wrote:
On Tue, 21 Jul 2020 00:42:29 +0000 (UTC), David Lesher
wb8foz@panix.com> wrote:

boB <boB@K7IQ.com> writes:

But I notice a dearth of 1-Wire ADC\'s.
Any idea why?


Not sure why there aren\'t any around ?

But we/I made our own for a battery shunt, in the negative lead A/D
monitor. Single wire is the power and two way data but only about 10
conversions per second in this case. The shunt is the second wire.

Used a 35 cent micro and I2C A/D. I don\'t see why you couldn\'t
address more than one of these on a single wire.

I suppose it all depends on how fast you need the data to be

Every few minutes will do.....

Common grounds are another obstacle. Hard to measure batteries in series...

Power each measuring unit locally from local battery and connect the
units in series into a single current loop using optoisolators. If
more or less standard UARTs are used, use two current loops. Connect a
scheduler transmitter to one loop and use it to address individual
measuring units (with Rx pins connected to the loop with
optoisolator). The addressed unit then sends measurement data by
interrupting the current flow in the other loop. A central monitor
then extract the data from that loop.

The drawback is that every unit must drive the Tx into Mark (20 mA)
Idle state to allow current pass from one station to the next. These
days with better optoisolators a much smaller loop current (say 2 mA)
could be used.

To get rid of the polling circuit, some CAN (Controller Area Network)
style current loop could be used (e.g. 2 mA recessive state and 0 V
dominant state) and let the nodes themselves handle the arbitration on
the same loop with both Tx and Rx isolators in the same loop for all
stations.

You seem to be reinventing the telegraph. lol

\"Reinventing\" ??

4-20 mA (and 0-20 mA) current loops are still in widespread use in
industrial systems.

I just described it in more detail so that some younger readers of
this newsgroup would also consider it.

>No need for two loops unless you want redundancy.

Half-duples over a single pair has been used for nearly a century with
teleprinters. There must be some conventions to allow only one end of
the link to transmit at a given time.

In a multidrop current loop, only one station is allowed to transmit
at once, thus arbitration between slaves (and optional master) is
needed.

The arbitration can be done by a master station in a single loop and
each slave must be able to distinguish between a master command and
some other slave sending out data (since it is heard by all slaves).

With optoisolators about 2 V voltage drop will occur in each Tx and
Rx. With a large number of nodes, say 30 (for a 30 x 12V =360 to 400 V
system) the current loop constant current loop supply must be at least
120 V (= 30 x 2 x 2V) with a half duplex system, which is too much for
some optoisolator transistor max Vce. Using two loops and the supply
voltage needs to be only 60 V (30 x 2 V), which more optoisolators can
handle.

 

[Jasen Betts]

On 2020-07-21, upsidedown@downunder.com <upsidedown@downunder.com> wrote:

On Tue, 21 Jul 2020 00:42:29 +0000 (UTC), David Lesher
wb8foz@panix.com> wrote:

boB <boB@K7IQ.com> writes:

But I notice a dearth of 1-Wire ADC\'s.
Any idea why?


Not sure why there aren\'t any around ?

But we/I made our own for a battery shunt, in the negative lead A/D
monitor. Single wire is the power and two way data but only about 10
conversions per second in this case. The shunt is the second wire.

Used a 35 cent micro and I2C A/D. I don\'t see why you couldn\'t
address more than one of these on a single wire.

I suppose it all depends on how fast you need the data to be

Every few minutes will do.....

Common grounds are another obstacle. Hard to measure batteries in series...

Power each measuring unit locally from local battery and connect the
units in series into a single current loop using optoisolators. If
more or less standard UARTs are used, use two current loops. Connect a
scheduler transmitter to one loop and use it to address individual
measuring units (with Rx pins connected to the loop with
optoisolator). The addressed unit then sends measurement data by
interrupting the current flow in the other loop. A central monitor
then extract the data from that loop.

Don\'t use optos, use capacitors. save lots of power.

You may need to use symbols with the same number of ones and zeros but
that shouldn\'t be a big problem.

--
Jasen.

 

[Jasen Betts]

On 2020-07-21, upsidedown@downunder.com <upsidedown@downunder.com> wrote:

On Tue, 21 Jul 2020 00:42:29 +0000 (UTC), David Lesher
wb8foz@panix.com> wrote:

boB <boB@K7IQ.com> writes:

But I notice a dearth of 1-Wire ADC\'s.
Any idea why?


Not sure why there aren\'t any around ?

But we/I made our own for a battery shunt, in the negative lead A/D
monitor. Single wire is the power and two way data but only about 10
conversions per second in this case. The shunt is the second wire.

Used a 35 cent micro and I2C A/D. I don\'t see why you couldn\'t
address more than one of these on a single wire.

I suppose it all depends on how fast you need the data to be

Every few minutes will do.....

Common grounds are another obstacle. Hard to measure batteries in series...

Power each measuring unit locally from local battery and connect the
units in series into a single current loop using optoisolators. If
more or less standard UARTs are used, use two current loops. Connect a
scheduler transmitter to one loop and use it to address individual
measuring units (with Rx pins connected to the loop with
optoisolator). The addressed unit then sends measurement data by
interrupting the current flow in the other loop. A central monitor
then extract the data from that loop.

Don\'t use optos, use capacitors. save lots of power.

You may need to use symbols with the same number of ones and zeros but
that shouldn\'t be a big problem.

--
Jasen.

 

[Jasen Betts]

On 2020-07-21, upsidedown@downunder.com <upsidedown@downunder.com> wrote:

On Tue, 21 Jul 2020 00:42:29 +0000 (UTC), David Lesher
wb8foz@panix.com> wrote:

boB <boB@K7IQ.com> writes:

But I notice a dearth of 1-Wire ADC\'s.
Any idea why?


Not sure why there aren\'t any around ?

But we/I made our own for a battery shunt, in the negative lead A/D
monitor. Single wire is the power and two way data but only about 10
conversions per second in this case. The shunt is the second wire.

Used a 35 cent micro and I2C A/D. I don\'t see why you couldn\'t
address more than one of these on a single wire.

I suppose it all depends on how fast you need the data to be

Every few minutes will do.....

Common grounds are another obstacle. Hard to measure batteries in series...

Power each measuring unit locally from local battery and connect the
units in series into a single current loop using optoisolators. If
more or less standard UARTs are used, use two current loops. Connect a
scheduler transmitter to one loop and use it to address individual
measuring units (with Rx pins connected to the loop with
optoisolator). The addressed unit then sends measurement data by
interrupting the current flow in the other loop. A central monitor
then extract the data from that loop.

Don\'t use optos, use capacitors. save lots of power.

You may need to use symbols with the same number of ones and zeros but
that shouldn\'t be a big problem.

--
Jasen.

 

[server]

On Wed, 22 Jul 2020 07:29:16 -0000 (UTC), Jasen Betts
<jasen@xnet.co.nz> wrote:

On 2020-07-21, upsidedown@downunder.com <upsidedown@downunder.com> wrote:
On Tue, 21 Jul 2020 00:42:29 +0000 (UTC), David Lesher
wb8foz@panix.com> wrote:

boB <boB@K7IQ.com> writes:

But I notice a dearth of 1-Wire ADC\'s.
Any idea why?


Not sure why there aren\'t any around ?

But we/I made our own for a battery shunt, in the negative lead A/D
monitor. Single wire is the power and two way data but only about 10
conversions per second in this case. The shunt is the second wire.

Used a 35 cent micro and I2C A/D. I don\'t see why you couldn\'t
address more than one of these on a single wire.

I suppose it all depends on how fast you need the data to be

Every few minutes will do.....

Common grounds are another obstacle. Hard to measure batteries in series...

Power each measuring unit locally from local battery and connect the
units in series into a single current loop using optoisolators. If
more or less standard UARTs are used, use two current loops. Connect a
scheduler transmitter to one loop and use it to address individual
measuring units (with Rx pins connected to the loop with
optoisolator). The addressed unit then sends measurement data by
interrupting the current flow in the other loop. A central monitor
then extract the data from that loop.

Don\'t use optos, use capacitors. save lots of power.

You may need to use symbols with the same number of ones and zeros but
that shouldn\'t be a big problem.

If you are going to use Manchester coding, you could also use
transformers for isolation, e.g. cheap Ethernet transferrers. Just
make sure you have steep edges, if the transformer low frequency
response is not very good.

When working close to big batteries, inductive or capacitance coupling
can be an issue, so you can\'t reduce the bus signal power too much.

A current loop optoisolator is not that bad. About 3 mW (1 mA from 3.3
V) from each node isolated power supply should be enough to control a
10 mA current loop.

 

[server]

On Wed, 22 Jul 2020 07:29:16 -0000 (UTC), Jasen Betts
<jasen@xnet.co.nz> wrote:

On 2020-07-21, upsidedown@downunder.com <upsidedown@downunder.com> wrote:
On Tue, 21 Jul 2020 00:42:29 +0000 (UTC), David Lesher
wb8foz@panix.com> wrote:

boB <boB@K7IQ.com> writes:

But I notice a dearth of 1-Wire ADC\'s.
Any idea why?


Not sure why there aren\'t any around ?

But we/I made our own for a battery shunt, in the negative lead A/D
monitor. Single wire is the power and two way data but only about 10
conversions per second in this case. The shunt is the second wire.

Used a 35 cent micro and I2C A/D. I don\'t see why you couldn\'t
address more than one of these on a single wire.

I suppose it all depends on how fast you need the data to be

Every few minutes will do.....

Common grounds are another obstacle. Hard to measure batteries in series...

Power each measuring unit locally from local battery and connect the
units in series into a single current loop using optoisolators. If
more or less standard UARTs are used, use two current loops. Connect a
scheduler transmitter to one loop and use it to address individual
measuring units (with Rx pins connected to the loop with
optoisolator). The addressed unit then sends measurement data by
interrupting the current flow in the other loop. A central monitor
then extract the data from that loop.

Don\'t use optos, use capacitors. save lots of power.

You may need to use symbols with the same number of ones and zeros but
that shouldn\'t be a big problem.

If you are going to use Manchester coding, you could also use
transformers for isolation, e.g. cheap Ethernet transferrers. Just
make sure you have steep edges, if the transformer low frequency
response is not very good.

When working close to big batteries, inductive or capacitance coupling
can be an issue, so you can\'t reduce the bus signal power too much.

A current loop optoisolator is not that bad. About 3 mW (1 mA from 3.3
V) from each node isolated power supply should be enough to control a
10 mA current loop.

 

[server]

On Wed, 22 Jul 2020 07:29:16 -0000 (UTC), Jasen Betts
<jasen@xnet.co.nz> wrote:

On 2020-07-21, upsidedown@downunder.com <upsidedown@downunder.com> wrote:
On Tue, 21 Jul 2020 00:42:29 +0000 (UTC), David Lesher
wb8foz@panix.com> wrote:

boB <boB@K7IQ.com> writes:

But I notice a dearth of 1-Wire ADC\'s.
Any idea why?


Not sure why there aren\'t any around ?

But we/I made our own for a battery shunt, in the negative lead A/D
monitor. Single wire is the power and two way data but only about 10
conversions per second in this case. The shunt is the second wire.

Used a 35 cent micro and I2C A/D. I don\'t see why you couldn\'t
address more than one of these on a single wire.

I suppose it all depends on how fast you need the data to be

Every few minutes will do.....

Common grounds are another obstacle. Hard to measure batteries in series...

Power each measuring unit locally from local battery and connect the
units in series into a single current loop using optoisolators. If
more or less standard UARTs are used, use two current loops. Connect a
scheduler transmitter to one loop and use it to address individual
measuring units (with Rx pins connected to the loop with
optoisolator). The addressed unit then sends measurement data by
interrupting the current flow in the other loop. A central monitor
then extract the data from that loop.

Don\'t use optos, use capacitors. save lots of power.

You may need to use symbols with the same number of ones and zeros but
that shouldn\'t be a big problem.

If you are going to use Manchester coding, you could also use
transformers for isolation, e.g. cheap Ethernet transferrers. Just
make sure you have steep edges, if the transformer low frequency
response is not very good.

When working close to big batteries, inductive or capacitance coupling
can be an issue, so you can\'t reduce the bus signal power too much.

A current loop optoisolator is not that bad. About 3 mW (1 mA from 3.3
V) from each node isolated power supply should be enough to control a
10 mA current loop.