DC Voltage level sensing

[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?



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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

 

[Winfield Hill]

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.


--
Thanks,
- Win

 

[Rick C]

On Sunday, November 10, 2019 at 2:36:32 PM UTC-5, Rick C wrote:

On Sunday, November 10, 2019 at 1:51:50 PM UTC-5, 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?

Many cars cut power to the cigarette lighter when off. I would simply detect that if your car is one that works this way.

If you are making this for a general application, you can use a 12 volt regulator, a PNP transistor and a diode. Connect the regulator normally with the diode base and emitter across the input (battery) to output, but with the diode in series to raise the threshold voltage... oh, and a resistor to limit the current. The STmicro L7812ABV has a tighter output voltage than many, 11.75 to 12.25 volts giving a threshold range around 12.95 to 13.5. The PNP will pull up to battery voltage when active, you can use an added NPN to turn that into a ground referenced output. Put the diode in the emitter leg to lower the pull up voltage a bit.

Oh yeah, you'll need a resistor on the regulator output to carry the base current since most linear regulators won't sink current on the output.

--

Rick C.

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[Rick C]

On Sunday, November 10, 2019 at 1:51:50 PM UTC-5, 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?

Many cars cut power to the cigarette lighter when off. I would simply detect that if your car is one that works this way.

If you are making this for a general application, you can use a 12 volt regulator, a PNP transistor and a diode. Connect the regulator normally with the diode base and emitter across the input (battery) to output, but with the diode in series to raise the threshold voltage... oh, and a resistor to limit the current. The STmicro L7812ABV has a tighter output voltage than many, 11.75 to 12.25 volts giving a threshold range around 12.95 to 13.5. The PNP will pull up to battery voltage when active, you can use an added NPN to turn that into a ground referenced output. Put the diode in the emitter leg to lower the pull up voltage a bit.

--

Rick C.

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

 

[Lasse Langwadt Christense]

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

 

[Phil Allison]

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.



...... Phil

 

[Martin Brown]

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.

--
Regards,
Martin Brown

 

[Martin Riddle]

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.

Cheers

 

[Rick C]

On Sunday, November 10, 2019 at 2:54:50 PM UTC-5, Phil Allison 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.

Why?

--

Rick C.

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

 

[whit3rd]

On Sunday, November 10, 2019 at 12:06:12 PM UTC-8, Lasse Langwadt Christensen wrote:

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

Maybe the 12V after the 'acc' switch would be better? It's high when ignition is on,
and can be user-invoked (with the key) with the motor not running,
but is always off when you leave the auto.

Dashcams with internal battery, that trickle-charge, ought NOT to rely on
generator operation for their function, else a car with bad fan belt becomes blind...
but maybe suppressing the trickle-charge is appropriate then.

 

[Lasse Langwadt Christense]

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

 

[Robert Baer]

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.

 

[Winfield Hill]

whit3rd wrote...

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

How easy is it to access that node?


--
Thanks,
- Win

 

[Phil Allison]

Rick the Know Nothing Cunt wrote:

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

** Think that is the wrong approach.

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

Why?


** The dopey OP has no need of a voltage monitor.

Only wants to know when the engine is running.

It's more direct to use charging current and allows a non
contact solution.

Nothing a code scrambling idiot would ever appreciate.


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

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



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

** Fools treat posters Qs literally.

And fuckwits like you.

Your idea requires a rather complex circuit compared to a simple
voltage regulator and transistor.

** No it isn't.

Geeze. Get real.

** You are a lunatic, get fucked.

No need to impose your ideas of what the requirements should be
to his idea of what he needs.

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

Nothing more.

I would point out that you often dictate your opinion on others,

** What do you imagine YOU just did ?

You have self awareness at all ??



...... Phil



..... Phil

 

[Rick C]

On Sunday, November 10, 2019 at 6:53:13 PM UTC-5, Phil Allison wrote:

Rick Cunt the Retard 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.

Why?


** The dopey OP has no need of a voltage monitor.

Only wants to know when the engine is running.

It's more direct to use charging current and allows a non contact solution.

Nothing a code scrambling idiot would ever appreciate.

Who cares about "direct"? What does that even mean exactly? He didn't ask for a non-contact solution. Most likely he needs 12 volts to power his circuit anyway.

Your idea requires a rather complex circuit compared to a simple voltage regulator and transistor. Geeze. Get real. No need to impose your ideas of what the requirements should be to his idea of what he needs.

I would point out that you often dictate your opinion on others, but then that might set you off on a ranting tear, swearing and blustering... which you likely will do anyway.

--

Rick C.

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

 

[Phil Allison]

Rick Cunt the Retard 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.

Why?

** The dopey OP has no need of a voltage monitor.

Only wants to know when the engine is running.

It's more direct to use charging current and allows a non contact solution.

Nothing a code scrambling idiot would ever appreciate.



...... Phil

 

[Phil Allison]

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.

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.

** 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.

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.

Cos you are an intolerant, fucking prick.



..... Phil

--

Rick C.

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

 

[Rick C]

On Sunday, November 10, 2019 at 7:37:24 PM UTC-5, Phil Allison wrote:

Rick the Know Nothing Cunt wrote:

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



** Think that is the wrong approach.

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

Why?


** The dopey OP has no need of a voltage monitor.

Only wants to know when the engine is running.

It's more direct to use charging current and allows a non
contact solution.

Nothing a code scrambling idiot would ever appreciate.


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, but if you mean the voltage indicates battery condition rather than whether the engine is on or not is simply wrong. The static voltage on a lead acid battery is around 12.7 volts when fully charged, less when the state of charge is lower. When charging as in a car, the voltage is significantly higher and around 13 volts is a reasonable threshold.

No need for the complication of trying to sense the charging current which will vary greatly. That's the nice thing of batteries, they are relatively constant voltage with it depending mostly on the charging status (charging or not) and a bit less on temperature.

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

** Fools treat posters Qs literally.

And fuckwits like you.

You are pretty funny actually. It's amazing that you think you are god's gift to electronics design. So much so that you can tell people what they *really* want even if you can't explain it.

Your idea requires a rather complex circuit compared to a simple
voltage regulator and transistor.


** No it isn't.


Geeze. Get real.


** You are a lunatic, get fucked.


No need to impose your ideas of what the requirements should be
to his idea of what he needs.


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

Nothing more.

Actually you didn't. You posted the barest thread of an idea with literally no real information on any useful details that are essential to the circuit working. Mostly because figuring out those details are what makes the circuit complex to design. Compared to a simple voltage regulator your approach is ridiculous.

I would point out that you often dictate your opinion on others,


** What do you imagine YOU just did ?

You have self awareness at all ??

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

--

Rick C.

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

 

[Phil Allison]

Rick the Know Nothing Cunt wrote:

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

** Think that is the wrong approach.

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

Why?


** The dopey OP has no need of a voltage monitor.

Only wants to know when the engine is running.

It's more direct to use charging current and allows a non
contact solution.

Nothing a code scrambling idiot would ever appreciate.


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

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



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

** Fools treat posters Qs literally.

And fuckwits like you.

Your idea requires a rather complex circuit compared to a simple
voltage regulator and transistor.

** No it isn't.

Geeze. Get real.

** You are a lunatic, get fucked.

No need to impose your ideas of what the requirements should be
to his idea of what he needs.

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

Nothing more.

I would point out that you often dictate your opinion on others,

** What do you imagine YOU just did ?

You have self awareness at all ??



...... Phil