LED display for gearindicator

[Nikke]

gear indicator circuit

Hi, Im new here and not so very experienced on small circuits, but I am an electrician, but I only work with HIGH Voltage.

Here is my project. Im going to make an gear indicator for my car.
I started to draw some prints on how it should work, but now I am stuck, just getting shorts everywhere.

This is how I want it to work.
I have 6 inputs from sensors. I want to translate every input to a digit on a LED display. (Image attached for the LED display I am using. Common Anod/Catod. That means that I can put + & - on whichever I want right?)

If input 1 is active; B and C should light up to form the digit 1. For that pin 9 and 7 should get power right?
If input 2 is active; A, B, E, G and D should light up to form the digit 2.
Etc...

Can someone draw a simple drawing to help me get on line? I want to make a simple and not so expensive display. Not with expensice PLC or Stamp's.

 

[Ante]

gear indicator schematics

You have to use diodes not to get shorts here.

Ante :roll:

 

[Nikke]

gear indicator schematic

Ok, serial on every pin? Maybe thats it. Am I that stupid!? :wink:

Like this? (see attachment)

 

[Nikke]

tip126 7-segment

I would need lots of diods then. If its like that.

So what type should I get? Rectifier, schothy, zener?

Also, is this how to connect the display? Plus on the pins for the digit I want to lit? Minus on the common anod/catod?

Also, the display takes uses max 11,2 volt to lit all lights, can I put 12-13 car volts on it or do I have to put an resistor into the circuit?

 

[Ante]

gear indicator scheme

What kind of display is it (any figures and letters on it)? Can it work without resistors in series with the elements? This is important, you can burn it if you make a mistake.
Yes you need lots of diodes but they are very cheap and you can use standard diodes small once like 1N4148.

Ante :roll:

 

[Nikke]

gearindicator

Its an 7 segment digit display. This one: https://www.elfa.se/elfa-bin/dyndok.pl?vat=0&dok=2019161.htm

Here is a datasheat: https://www.elfa.se/pdf/75/07506421.pdf

I cant find any info if I need resistors or not? I just can see that every element uses max 20 mA each. And the displays segments uses operating voltage from 6.8 to 11.2 V. The dot on the display uses: 3.4 to 5.6 V.

So simple; I put + on the pins for the segments I want to light up, and - on the common cathodes. Both of them?

 

[Ante]

big led common cathode

I would put resistors in, one for each segment 120 ohm for the segments and 470 ohm for the point if you are going to use it. You have to ground (-) the common cathode pin (1) and connect the anodes via resistors and diodes to positive (+) coming from the gear sensors.

Heja Sverige!

 

[Nikke]

ok, just to keep the voltage not to high. I'll also put a smaller fuse, just in case.

So just pin 1 need minus? Not pin 5 too? Ok.

Thanks for your help!

 

[Ante]

Here is an example of the circuit for the first three gears. However it is not the same display as the one you have. The resistors are 120 ohm and the diodes are 1N4148 or similar.

Ante :roll:

 

[Nikke]

Great! I've understand you right. Its like I drew it.

 

[Ante]

Nikke,

Please let us know how it turns out.

Ante :roll:

 

[Nikke]

Sure,

I need help making another function.
When no sensor is activated, aka no input, I want the display to show an N (for neutral). Some sort of inverse circuit. So when a sensor is activated the N function should be away.
Is there a way to use transistors and diods to make that? EDIT: Maybe its easiest to use any simple logic gate-circuit with inverted function.

Also can I put capacitators on each of the sensor wires before the diods, to make a sort of delay so the N doesnt show up to quickly? How big do I need to get 0,5-1 second delay?

EDIT: I drew a quick layout, will it work? (I havent drewn the wires for the other digits)
I used the 74C00/Fch which handles +3 to +15 V. The inputs can be max 30 % of 15 V. Please make suggestions on how to improve it.

 

[Nikke]

Here is the circuit of the Neutral function. Will it work??

 

[Ante]

Nikke,

You don't need all that stuff. I think this little circuit will do the job. But I am curious; which segments do you chose to make an “N”? I think if I where to make something like this I would make the segments A, B, G and F walk in a circle while in neutral, kind a cool don’t you think?

Ante :roll:

 

[Nikke]

E, G and C, is the ones I want to use, making an "n".

It looks quite the same as mine, can you explain that circuit? Q1 does open (cut off the light to n) when positive income from the sensors? What transistor is that? What does the resitors do, protect Q1?

What if I put an capacitor before R1? Do I get a bit of delay before the "n" shows up?

 

[Ante]

The resistors are biasing the transistor. R2 “opens” the transistor as long as there is no signal from R1 via one of the diodes. When a gear is engaged the positive from the diode through R1 will shut down Q1 and the N is gone. The transistor is a Darlington type TIP 127 it can be replaced with many others with similar data. If you want a delay for N just put a capacitor parallel with R2.

Ante :roll:

 

[Nikke]

Will this transistor work? TIP126/STM PNP 65 W 80 V Max (e-c) 5 A.
Should I put + on the emitter and out to display on the collector??

How big capacitor should I use? I want that the gear indications stays abit longer before the n shows up. Just a second.

Here is the beta 1 drawing for the gear indicator circuit.
Please check it for errors and improvements.

 

[kukurigu]

By the way: Which kind of sensors do you use for the gears? Do you have them implemented or you will do your own?

 

[Nikke]

Im making my own sensors, because sensors or switches are very expensive.
Its more of a simple circuit breaker.

This is how i think it would be, but final result is never like the first thougt.
See for your self:

 

[Ante]

Yes Nikke, the TIP126 should do fine here. As you can see in the schematic “neutral” I posted; positive to the emitter and the load at the collector side. About the time delay, try with 100uF and then higher if you need longer time. Remember the polarity when adding the capacitor across R2.

Ante :roll: