So, to be cleat:

Left Input 0 V, Right input 0 V > Silent
Left Input 0 V, Right input 12 V > Silent
Left Input 12 V, Right input 0 V > Silent
Left Input 12 V, Right input 12 V > Beep

Correct?

ak

That was my guess as well, based on the guess that it was a car with a 12 volt system and frame as negative return for the lights. Thus my guess that a light being on was with +12 volts to be sensed. I also guessed that with no voltage applied, the internal resistance of the indicator would pull that line toward zero volts. and thus pull that logic input toward zero. That must happen for my logic scheme to work as required.

 

I was thinking of trying this instead of tge uln2004 because it is already on a pcb and easy wired.
https://www.ebay.co.uk/itm/22593104...4g9lmQUQ8O&var=&widget_ver=artemis&media=COPY
Thank you.

If you do this, use an NMOS version of this driver. It will keep the current drain on the input signal to minimum.

https://www.ti.com/product/TPL7407LA

 

If you do this, use an NMOS version of this driver. It will keep the current drain on the input signal to minimum.

Note that the TPL part requires a power source for its internal circuitry. It is not a drop-in replacement in all applications.

ak

 

I already provided the circuit description in post #3, and then A.K. provided the actual circuit, as described, in post#9. So what is the motivation for suggesting all sorts of much more complex versions??
OR was my description not clear?? The added advantage is that it reduces the possibility of damage caused by random voltage spikes that sometimes happen on automotive electrical systems.

 

I already provided the circuit description in post #3, and then A.K. provided the actual circuit, as described, in post#9. So what is the motivation for suggesting all sorts of much more complex versions??
OR was my description not clear?? The added advantage is that it reduces the possibility of damage caused by random voltage spikes that sometimes happen on automotive electrical systems.

A drawing would have probably helped.

 

Are the flasher bulbs LED or incandescent?

ak

 

A drawing would have probably helped.

DID YOU EVEN LOOK at the circuit AK posted in #9??? AK added a couple resistors and a diode, but otherwise exactly the operation of what I described in post #3. Isit that difficult to visualize a circuit with only 4 or 5 parts???

 

DID YOU EVEN LOOK at the circuit AK posted in #9???

OK, sparky, calm down. Text-to-schematic is a learned skill that requires time and experience to develop. It is clear from the language in post #1 that the TS is not fluent in circuit-speak. I got part way through your description, gave up, and posted my own designs (based on some work at a TV station in the 70's). That they are similar is pure coincidence.

ak

 

OK, sparky, calm down. Text-to-schematic is a learned skill that requires time and experience to develop. It is clear from the language in post #1 that the TS is not fluent in circuit-speak. I got part way through your description, gave up, and posted my own designs (based on some work at a TV station in the 70's). That they are similar is pure coincidence.

ak

Soz, been quite ill today. Non cancer Steroid induced hiccups (DIH). Havent felt like looking into this much.
Thank you all for your suggestions.

 

DID YOU EVEN LOOK at the circuit AK posted in #9???

I'm not the TS.

AK added a couple resistors and a diode, but otherwise exactly the operation of what I described in post #3.

If you want credit for "your" design, a drawing might have helped.

Isit that difficult to visualize a circuit with only 4 or 5 parts???

It might be for some posters.

 

There is nothing in this thread to indicate that that is a problem. It would really help to know what the "indicators" are.

Here is a 2-input AND circuit that does not source current out its inputs.

ak

View attachment 320959

What is happening with the two NAND gates not connected to anything.

 

My assumption about "indicators required that they would be devices that exhibited a resistance to the negative(ground) connection so that they would effect a connection to ground when they were not powered. For my proposed logic solution to work, the indicators have to conduct enough current for the diodes to be biased into conduction. Thus they could be filament type lights or LED type lights, but not gas-discharge types, nor lights with current regulators internal.

 

What is happening with the two NAND gates not connected to anything.

Logic gates, and particularly CMOS logic gates, must have all unused inputs terminated in defined states. The outputs are fine when left floating, and in fact leaving them unconnected reduces circuit power. Leaving inputs floating can *increase* circuit power because both output transistors come on partially, creating a current path from Vcc to GND. In older gate designs, the current can be a large enough to reduce the long-term reliability of the part.

ak

 

Logic gates, and particularly CMOS logic gates, must have all unused inputs terminated in defined states. The outputs are fine when left floating, and in fact leaving them unconnected reduces circuit power. Leaving inputs floating can *increase* circuit power because both output transistors come on partially, creating a current path from Vcc to GND. In older gate designs, the current can be a large enough to reduce the long-term reliability of the part.

ak

Looks like I need pullup or down resistors on pins 1&2 of the 4011 cos it is chipping rapidly.

 

Looks like I need pullup or down resistors on pins 1&2 of the 4011 cos it is chipping rapidly.

Looks a bit of a dogs breakfast but function over form

 

The electrical nature of the two inputs still are not known. Pulled up to 12 V, pulled down to GND, open circuit, medium-impedance to an unknown voltage - ??? Pulling the two inputs down to GND with a 10K or 100 K resistor will assure that if either or both inputs are floating, they will not contribute to a false alarm.

ak

 

The electrical nature of the two inputs still are not know. Pulled up to 12 V, pulled down to GND, open circuit, medium-impedance to an unknown voltage - ??? Pulling the two inputs down to GND with a 10K or 100 K resistor will assure that if either or both inputs are floating, they will not contribute to a false alarm.

ak

In an automotive exterior lights application, except for headlights, which sometimes have goofy DRL circuits, other lights all return to chassis common and all are open circuited source, internal resistive pull down when not lighted. So my original suggestion with diode logic holds.
See posts #3 and #9, and #32 for details.
Not meaning to be harsh or nasty, but some things are rather standard.

 

Not meaning to be harsh or nasty, but I'm aware of how cars were wired in the 1950's. Both my 17 year old car and my wife's brand new car have two wire harness connections to each light, and neither one is hard-tied to the chassis.

At this point, we don't know the year, make, or model, let alone how the lights are controlled.

ak

 

Automotive Wiring-Harness-Grounds are normally spliced into each other "somewhat" locally,
then only "pop-out" of the Harness at a convenient location where they can be attached to the Body.
Almost nothing is Grounded right next to the respective Load(s), where it would be much more obvious.

Making assumptions, without a Factory-Wiring-Harness-Schematic, is really a time waster.
It's hard-enough to figure-out when You actually DO have a Schematic right in front of You.

Automotive-Wiring-Harnesses are designed for the fastest installation-time on the Assembly-Line,
and they don't care if You can figure-out what they were thinking when they designed it.
.
.
.

 

Not meaning to be harsh or nasty, but I'm aware of how cars were wired in the 1950's. Both my 17 year old car and my wife's brand new car have two wire harness connections to each light, and neither one is hard-tied to the chassis.

At this point, we don't know the year, make, or model, let alone how the lights are controlled.

ak

Of course they had two wires! one for the turn signal and one for the"parking " light operation. And in back as well, two wires plus the base ground. One was the "tail light" and the other was the STOP/Turn signal light. At least that it was done on most of the cars made for use in the USA. Other countries may have been different. Of course, that was after turn signals became common standard equipment. That is why the turn signal switch had so many wires. And it also lead to issues with poor grounds on one light causing confusing symptoms.

So just because the light had two wires did not mean that one of them was the return (ground) side. The third wire, the common return wire, was present on those cars that had plastic grills with the lights mounted in them. And the light bulbs had two buttons on the bottom, with the brass base being the grounded common.

And I have a bit more familiarity with vehicle wire harnesses because at one job I was programming and supporting the electrical testers for vehicle wiring installations. So I was intimately familiar with EVERY DETAIL of the wiring system of s few different products from one of the "Big Three" companies. I became an expert at programming in one language that was obsoleted by the next version of testers that used a much faster computer,running windows, which was vastly slower then the older testers running a 6809 processor with a 2 MHZ clock frequency, versus the 33 MHZ clock of the replacement tester computers.