DC Voltage level sensing

[Winfield Hill]

Winfield Hill wrote...

Cursitor Doom wrote...

How most reliably to sense when the battery voltage
exceeds 13V so a dashcam can be activated?

Get a TL431 datasheet. Buy an TL431ACLP, in TO-92
package. Add three resistors and a p-channel MOSFET,
maybe an IRF9540N in TO-220, and you're good to go.

Except, to see motor operating, set threshold to 13.5V.
But, these days lots of cars take any opportunity to
turn off ICE engine, so ignition key power is better.


--
Thanks,
- Win

 

[Tom Del Rosso]

Cursitor Doom wrote:

Greetings, Gentlemen,

What's the simplest way of implementing this:

The 'quiescent voltage' (so to speak) of a car battery is typically
12.4V. With the engine running, however, this rises to 14V due to the
charging current from the alternator. How most reliably to sense when
the battery voltage exceeds 13V so a dashcam can be activated?

If you have a car like mine, where the lighter socket is always on,
maybe it would be better to move its connection to the switched power
bus. Then you could turn it on in stealth mode without starting the
engine.

 

On Sun, 10 Nov 2019 14:27:53 -0800 (PST), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

sřndag den 10. november 2019 kl. 23.21.24 UTC+1 skrev Winfield Hill:
whit3rd wrote...

Maybe the 12V after the 'acc' switch would be better?

How easy is it to access that node?


the cigarette lighter might be on it, or on the radio connector

It'll certainly be in the fuse panel.

 

On Sun, 10 Nov 2019 21:41:29 +0000, Martin Brown
<'''newspam'''@nezumi.demon.co.uk> wrote:

On 10/11/2019 18:51, Cursitor Doom wrote:
Greetings, Gentlemen,

What's the simplest way of implementing this:

The 'quiescent voltage' (so to speak) of a car battery is typically
12.4V. With the engine running, however, this rises to 14V due to the
charging current from the alternator. How most reliably to sense when the
battery voltage exceeds 13V so a dashcam can be activated?

Take the power from the cigarette lighter feed.

That's not reliable. Mine is always on. The AUX circuit is needed.
Sometimes there is a switched AUX outlet (looks like a cigar lighter
but it's not ;-) somewhere. Might also try a USB port.

 

On Sun, 10 Nov 2019 16:16:11 -0500, Martin Riddle
<martin_ridd@verizon.net> wrote:

On Sun, 10 Nov 2019 12:06:07 -0800 (PST), Lasse Langwadt Christensen
langwadt@fonz.dk> wrote:

sřndag den 10. november 2019 kl. 19.51.50 UTC+1 skrev Cursitor Doom:
Greetings, Gentlemen,

What's the simplest way of implementing this:

The 'quiescent voltage' (so to speak) of a car battery is typically
12.4V. With the engine running, however, this rises to 14V due to the
charging current from the alternator. How most reliably to sense when the
battery voltage exceeds 13V so a dashcam can be activated?


use 12V after the ignition switch, KL15 in DIN standard


Piggy back off the Fuel pump power. THe pump shuts off if the engine
is not running after x seconds if the ignition is on.

Tap the AUX power or the OBD-II port.

 

On Sun, 10 Nov 2019 14:44:18 -0800, Robert Baer
<robertbaer@localnet.com> wrote:

tabbypurr@gmail.com wrote:
On Sunday, 10 November 2019 18:51:50 UTC, Cursitor Doom wrote:
Greetings, Gentlemen,

What's the simplest way of implementing this:

The 'quiescent voltage' (so to speak) of a car battery is typically
12.4V. With the engine running, however, this rises to 14V due to the
charging current from the alternator. How most reliably to sense when the
battery voltage exceeds 13V so a dashcam can be activated?

comparator. Manually adjusted relays were once used but electronics be more reliable, assuming it's designed to handle car electric nasties. You could also use the charging light.


NT

"Electronics be more reliable"?
In a rather hot, almost still air environment?
When cars are expected to run reliably in a desert?
Give me a break.

Absolutely. Cars are far more reliable now than they ever have been,
despite the one, with many zeros, times the number of transistors in
them. It's called "design".

 

[Rick C]

On Sunday, November 10, 2019 at 8:22:55 PM UTC-5, Phil Allison wrote:

Rick Cunt is a Stupid Fucking Nut case wrote:
------------------------------------------


Who cares about "direct"? What does that even mean exactly?


** Means battery condition, hence voltage, becomes non critical.

Your lack of proper sentence construction makes it hard to understand exactly what you are trying to say,


** You rampant autism ruins your comprehension.


No need for the complication of trying to sense the charging current which will vary greatly.

** Only need to sense polarity plus have some threshold.

Yep, which is a much different and more complex solution than the one I proposed, plus it has to be done under the hood rather than under the dash or even through the cigarette lighter socket... opps, I mean the accessory power outlet.

He didn't ask for a non-contact solution.

** Fools treat posters Qs literally.

And fuckwits like you.

You are pretty funny actually.


** Look, I do my best in face of many trolling, fucking assholes like you..

But you are so incapable of admitting when you have failed.

** I posted a good solution to the *problem*, as posed.

Nothing more.

Actually you didn't.


** Yes I did.

If the OP likes the concept, he can ask for more info.

Don't hold your breath.

I'm not the one telling the OP his ideas of what he wants are wrong.


** Nor I.

You are the one telling ME and NG I am wrong, when I am not.

If you think the OP asked how to sense current rather than voltage you are wrong.

It's actually a bit unclear exactly when he wants the dash camera to be on but it is very possible waiting for the engine to be started is not enough.

Regardless, a simple voltage measurement from a cigarette lighter socket will tell him if the accessory is on (assuming the circuit is wired that way) or if the engine is running. He can decide if he wants to run the camera or not and when. Your method only tells him if the engine is running.


> Cos you are an intolerant, fucking prick.

And you are rather entertaining. It's amusing to wind you up and let you rant. Odd that you accuse others of having all your own flaws.

--

Rick C.

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

 

[Rick C]

On Sunday, November 10, 2019 at 9:01:48 PM UTC-5, k...@notreal.com wrote:

On Sun, 10 Nov 2019 14:27:53 -0800 (PST), Lasse Langwadt Christensen
langwadt@fonz.dk> wrote:

søndag den 10. november 2019 kl. 23.21.24 UTC+1 skrev Winfield Hill:
whit3rd wrote...

Maybe the 12V after the 'acc' switch would be better?

How easy is it to access that node?


the cigarette lighter might be on it, or on the radio connector

It'll certainly be in the fuse panel.

I was looking for a fuse puller the other day and found they make fuse sockets that plug in place of the fuse, with a socket for the fuse, plus taps for external connections. Don't recall if that was on Alibaba or eBay.

--

Rick C.

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

 

[Phil Allison]

Some Rampant Code Scribling IDIOT:

-----------------------------------

** You rampant autism ruins your comprehension.

** Only need to sense polarity plus have some threshold.

Yep, which is a much different and more complex solution

** It's actually simpler.


> Regardless, a simple voltage measurement from a cigarette lighter socket will tell him if the accessory is on (assuming the circuit is wired that way) or if the engine is running.

** No it wont, not reliably.

Battery voltage rises when on charge for some time, not instantly like current.

The voltage at an outlet varies under load.

Using charging current is far more precise.



...... Phil

 

[whit3rd]

On Sunday, November 10, 2019 at 2:21:24 PM UTC-8, Winfield Hill wrote:

whit3rd wrote...

Maybe the 12V after the 'acc' switch would be better?

How easy is it to access that node?

If you can find the fuse block (I've done that) and probe it (almost
impossible, my car hasn't enough room for me to get my head where I can
see the darned thing without a mirror in one hand, which leaves my
other two hands free for the flashlight and the meter probe),
then you can look for an unpopulated fuse position, and tap in there.

Or, splice into the radio power wire, which means sharing the fuse
capacity of the radio. Some radios have more than one power lead
(one for the clock).

 

[Phil Allison]

Some Rampant Code Scribling IDIOT:


It's so simple you can't even describe the circuit in any detail.

** Not necessary yet.

Try it, you will find it is a lot worse than a 3 pin voltage regulator,
a transistor and a resistor.

** A poor solution, battery condition dependent.

** No it wont, not reliably.

Battery voltage rises when on charge for some time, not instantly like current.

Of course the battery voltage rises instantaneously when charging.

** It does fucking not.

Takes time to put charge in a battery when it is low.

The voltage at an outlet varies under load.

Using charging current is far more precise.

"Precise"???

** You are incredibly thick.

Must be one of 'dem PIC programmer morons.

All bullshit, zero electronic knowledge.

Plus a king size fucking asshole.



...... Phil

 

[Rick C]

On Sunday, November 10, 2019 at 9:29:26 PM UTC-5, Phil Allison wrote:

Some Rampant Code Scribling IDIOT:

-----------------------------------


** You rampant autism ruins your comprehension.

** Only need to sense polarity plus have some threshold.

Yep, which is a much different and more complex solution

** It's actually simpler.

It's so simple you can't even describe the circuit in any detail. Try it, you will find it is a lot worse than a 3 pin voltage regulator, a transistor and a resistor.

Regardless, a simple voltage measurement from a cigarette lighter socket will tell him if the accessory is on (assuming the circuit is wired that way) or if the engine is running.

** No it wont, not reliably.

Battery voltage rises when on charge for some time, not instantly like current.

Of course the battery voltage rises instantaneously when charging. That's why a battery at rest is around 12.7 and >13.5 when charging with the exact value depending on the current. Not sure what you are trying to say, but you didn't do it very well.

The voltage at an outlet varies under load.

Using charging current is far more precise.

"Precise"??? This is a threshold measurement. Car on or off. It needs to be accurate enough to tell the difference. Everything else you talk about is blustering.

<13 volts is engine off. >13.5 volts is engine running. The actual threshold can be anywhere in that range. Additional precision is wasted effort.

Why don't you give up before you embarrass yourself further?

--

Rick C.

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

 

[Rick C]

On Sunday, November 10, 2019 at 10:14:36 PM UTC-5, Phil Allison wrote:

Some Rampant Code Scribling IDIOT:


It's so simple you can't even describe the circuit in any detail.


** Not necessary yet.

There's also a lack of... understanding on your part. You can probably work it out eventually, but right now you don't even know how to do it.

Try it, you will find it is a lot worse than a 3 pin voltage regulator,
a transistor and a resistor.


** A poor solution, battery condition dependent.

Not in any important way. The battery will rise to the voltage imposed by the alternator unless it is nearly dead in which case you have other problems than your dash cam not being turned on.

** No it wont, not reliably.

Battery voltage rises when on charge for some time, not instantly like current.

Of course the battery voltage rises instantaneously when charging.


** It does fucking not.

Takes time to put charge in a battery when it is low.

What a maroon. I have been charging batteries for the last couple of days and I always see a current dependent change in battery voltage when charging. The only things that doesn't change voltage with changes in current are superconductors. Every battery has an internal resistance which is not necessarily from the mechanical parts. It has to do with the chemistry.

The voltage at an outlet varies under load.

Using charging current is far more precise.

"Precise"???



** You are incredibly thick.

Must be one of 'dem PIC programmer morons.

All bullshit, zero electronic knowledge.

Plus a king size fucking asshole.

It is not at all uncommon for technicians to lash out when they are caught with their pants down. You don't understand batteries very well, but that's ok. You just need some more experience with them and then I'm sure you will eventually learn.

--

Rick C.

-+- Get 2,000 miles of free Supercharging
-+- Tesla referral code - https://ts.la/richard11209

 

[Jasen Betts]

On 2019-11-10, Cursitor Doom <curd@notformail.com> wrote:

Greetings, Gentlemen,

What's the simplest way of implementing this:

The 'quiescent voltage' (so to speak) of a car battery is typically
12.4V. With the engine running, however, this rises to 14V due to the
charging current from the alternator. How most reliably to sense when the
battery voltage exceeds 13V so a dashcam can be activated?

TL341 seems rated for automotive use.

http://www.ti.com/lit/ds/symlink/tl431.pdf figure 25




--
When I tried casting out nines I made a hash of it.

 

[Jasen Betts]

On 2019-11-10, Winfield Hill <winfieldhill@yahoo.com> wrote:

whit3rd wrote...

Maybe the 12V after the 'acc' switch would be better?

How easy is it to access that node?

It's typically in the steering column, and in the fuse panel, also at the back
of the radio etc... the wiring diagram for the automoibile in question will
have all the answers.

--
When I tried casting out nines I made a hash of it.

 

[Jasen Betts]

On 2019-11-10, Phil Allison <pallison49@gmail.com> wrote:

Cursitor Doom wrote:

----------------------


The 'quiescent voltage' (so to speak) of a car battery is typically
12.4V. With the engine running, however, this rises to 14V due to the
charging current from the alternator. How most reliably to sense when the
battery voltage exceeds 13V so a dashcam can be activated?


** Think that is the wrong approach.

Better to detect if the battery is being charged with a significant current.

Using say a Hall Effect ( non contact) device set up so that it is both level and polarity sensitive.

The it will need to latch and have some time out delay.

I suspect that he wants to tap into the dome light circuit (which is
always hot and is available near the rear-view mirror mounting in many
cars)

Otherwise It's easier to tap into the accessory or ignition
circuit behind the dash, and not bother with sensing anything...


--
When I tried casting out nines I made a hash of it.

 

[Jan Panteltje]

Greetings, Gentlemen,

What's the simplest way of implementing this:

The 'quiescent voltage' (so to speak) of a car battery is typically
12.4V. With the engine running, however, this rises to 14V due to the
charging current from the alternator. How most reliably to sense when the
battery voltage exceeds 13V so a dashcam can be activated?

Any comparator will do, but you need a LOT of filtering in a car
as the battery voltage is not clean.


I would use a PIC, as most have and ADC and 2 hardare comparators.
But any 12V or so opamp will do.

The PIC would also display battary voltage..

 

[Jan Panteltje]

Eye wrote
...Any comparator will do, but you need a LOT of filtering in a car
...as the battery voltage is not clean.

Hysteresis, I forgot hysteresis,
else your -cam will flapper on / off.

 

[Jeff Layman]

On 10/11/19 18:51, Cursitor Doom wrote:

Greetings, Gentlemen,

What's the simplest way of implementing this:

The 'quiescent voltage' (so to speak) of a car battery is typically
12.4V. With the engine running, however, this rises to 14V due to the
charging current from the alternator. How most reliably to sense when the
battery voltage exceeds 13V so a dashcam can be activated?

Why do you want the dashcam to work only when the engine is running? If
you are parked listening to the radio, setting the satnav, or whatever
with the engine off, and somebody drives into you, wouldn't you want
that recorded?

My dashcam plugs into one of the USB sockets on my car, and operates (as
others have suggested) when in "Aux" mode without the engine running. If
possible I suggest you do the same.

--

Jeff

 

[Lasse Langwadt Christense]

mandag den 11. november 2019 kl. 03.00.57 UTC+1 skrev k...@notreal.com:

On Sun, 10 Nov 2019 16:16:11 -0500, Martin Riddle
martin_ridd@verizon.net> wrote:

On Sun, 10 Nov 2019 12:06:07 -0800 (PST), Lasse Langwadt Christensen
langwadt@fonz.dk> wrote:

søndag den 10. november 2019 kl. 19.51.50 UTC+1 skrev Cursitor Doom:
Greetings, Gentlemen,

What's the simplest way of implementing this:

The 'quiescent voltage' (so to speak) of a car battery is typically
12.4V. With the engine running, however, this rises to 14V due to the
charging current from the alternator. How most reliably to sense when the
battery voltage exceeds 13V so a dashcam can be activated?


use 12V after the ignition switch, KL15 in DIN standard


Piggy back off the Fuel pump power. THe pump shuts off if the engine
is not running after x seconds if the ignition is on.

Tap the AUX power or the OBD-II port.

OBD-II only specifies an always on +12V battery, though I believe audi/vw puts ignition ON on one of the unused pins