Learning from this Zener Circuit

Thread Starter

beeson76

Joined Apr 19, 2010
193
I just made this circuit up. It has no purpose at all. Just made it to learn about zener diodes:):)

Is a zener diode (all 4 of them) good in this circuit. I have 4 push buttons that I would like to light just a simple led up that corresponds with that push button. It seems to be working ok, but I cannot get the LEDS to be completely "off" or when I hit some buttons, some LEDS come on half way. Im assuming it has to do with the value of the Zeners I am using. I am using 1n5233 Zener for all of them. Im assumming those values are wrong.

But what I would like to happen is that the LEDS are completely off, and then when I push switches 1, 2, 3, 4 only that LED lights.

Any help is greatly appreciated:):)

Thanks Guys
Mike
 

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Zeeus

Joined Apr 17, 2019
421
I just made this circuit up. It has no purpose at all. Just made it to learn about zener diodes:):)

Is a zener diode (all 4 of them) good in this circuit. I have 4 push buttons that I would like to light just a simple led up that corresponds with that push button. It seems to be working ok, but I cannot get the LEDS to be completely "off" or when I hit some buttons, some LEDS come on half way. Im assuming it has to do with the value of the Zeners I am using. I am using 1n5233 Zener for all of them. Im assumming those values are wrong.

But what I would like to happen is that the LEDS are completely off, and then when I push switches 1, 2, 3, 4 only that LED lights.

Any help is greatly appreciated:):)

Thanks Guys
Mike
Sure your diagram is same as what you have?
Don't know much but looks like no led will come on with your diagram
 

KeithWalker

Joined Jul 10, 2017
417
I just made this circuit up. It has no purpose at all. Just made it to learn about zener diodes:):)

Is a zener diode (all 4 of them) good in this circuit. I have 4 push buttons that I would like to light just a simple led up that corresponds with that push button. It seems to be working ok, but I cannot get the LEDS to be completely "off" or when I hit some buttons, some LEDS come on half way. Im assuming it has to do with the value of the Zeners I am using. I am using 1n5233 Zener for all of them. Im assumming those values are wrong.

But what I would like to happen is that the LEDS are completely off, and then when I push switches 1, 2, 3, 4 only that LED lights.

Any help is greatly appreciated:):)

Thanks Guys
Mike
Your circuit looks like an excellent way to damage the LEDs. When you push a button, you are applying the full battery voltage across the LED in series with a six volt zener diode. The current is only limited by the internal resistance of the battery. You will get around three volts applied across the led. That is not a nice thing to do.

Why not just connect one side of the push buttons to battery + and connect a led in series with a suitable current limiting resistor between the other side of each push button to the battery -. That way, each led will remain off until it's associated button is pressed.
If you are using regular indicator LEDs, 10 Ma should be sufficient current to light them so use 820 ohm resistors.
 

Thread Starter

beeson76

Joined Apr 19, 2010
193
Thanks Guys for the answers. I appreciate it very much:):)

Didn't realize it Keith until you noted it to me. You are right!! I have not limiting resistors to my LEDS. So I have to figure that out.

What I would like to do with this circuit is in steps. I would first of all like to create a visual way of knowing which button I press....hence the LEDs. I could do it like you suggested Keith which would be very simple. In time though I want to see if I can tell which buttons I press using the resistance of the circuit. For example with no buttons pressed I have a resistance of about 3540 Ohms. When I press button swtich 4 I have about 1735 Ohms...and so on and so forth. I can easily tell using a multimeter, but I would like to not use a multimeter and do the visual form such as LED.

Hope that makes sense:):) In time I would like to eventually get it set up using a LCD telling which Switch was pressed based on the reading of the Ohms. But I gotta get the basics first:):)

Thanks guys for the answers and the help. I really do appreciate it very much:):)
 

narkeleptk

Joined Mar 11, 2019
373
I don't know circuits that well but I don't really understand what you want to accomplish. Why do you have voltage dividers for when button is off but full power when button is pressed? Are you trying to illuminate all the lights dimly and then when button is pressed one gets brighter? Why do you even need the zeners if you just want them on or off?
For LEDS off unless the button is pressed you only need the following.
.......led......R.........S (normally open/closed when pushed)
(+)---|<---/\/\/\/\----_-_----(-)
(+)---|<---/\/\/\/\----_-_----(-)
(+)---|<---/\/\/\/\----_-_----(-)
(+)---|<---/\/\/\/\----_-_----(-)
(+)---|<---/\/\/\/\----_-_----(-)
 

Thread Starter

beeson76

Joined Apr 19, 2010
193
Thanks Narkeleptk for the reply.

At this moment I started with the switch/resistor circuit. When attaching the multimeter to that simple circuit I was was able to tell which switch I pressed cause I could read the ohm reading on the multimeter. For example:
SW1 1.735 Ohm
SW2 928 Ohm
SW3 518 Ohm
SW4 244 Ohm

Just a simple basic circuit just reading the ohms when a switch was pressed. I then started thinking that a visual representation of some kind would be cool. So I thought of LEDs. But when I attached the LED's they were very inconsistent about one lighting, or all lighting, or some being dim and never shutting off. So I started thinking that maybe Zeners would be a good use for this circuit cause I kinda read that could limit voltage:):)

This is just a case of someone with just enough knowledge to do a lot of blowing up of LEDs:):) Don't really understand the concept of Zeners, but I am wanting to learn:):) and this may not even be a good circuit to use Zener in.

Im just simply wondering if I can somehow use 4 LEDs to show which switch is pressed while keeping the 5 resistors in the circuit. Not Lighting at all (even dimly) until a button is pressed...using whatever I have to use:):)

Thanks again for the help:):)
 

dl324

Joined Mar 30, 2015
8,950
Just a simple basic circuit just reading the ohms when a switch was pressed. I then started thinking that a visual representation of some kind would be cool. So I thought of LEDs. But when I attached the LED's they were very inconsistent about one lighting, or all lighting, or some being dim and never shutting off. So I started thinking that maybe Zeners would be a good use for this circuit cause I kinda read that could limit voltage
This circuit might do what you want:
upload_2019-7-8_10-43-39.png
The LEDs will light independently only when their corresponding switch is closed. Resistor values would depend on whether the color(s) of the LEDs, and the brightness you want.

What were you trying to do with the circuit you posted?
upload_2019-7-8_10-45-39.png
 

narkeleptk

Joined Mar 11, 2019
373
Okay I see what you mean now you originally was playing with voltage divider and then wanted to throw in domr LEDs to light which button you were pushing and thought maybe the zeiner's would come into play here

your original circuit makes a little more sense now though it still will not work and you will need to study and play a little bit more with it
 

Thread Starter

beeson76

Joined Apr 19, 2010
193
Thanks DL324:):)

This was my original circuit. I was just playing around and wanted to see the ohms that each switch would display. (Please see the attachment)

I then got to thinking, I wonder if I can keep this circuit and use a visual aid to help me see what switch was pressed without using the multimeter. Of course it wont tell me the ohms but It could tell me which switch was pressed. So I attached some LEDs and when I started pressing switches, the LEDs were very inconsistent. Some would dimly light, some switches would allow all to light.

So I was just wondering if there was anyway of keeping the Ohms the same for each switch but light the corresponding LED at the same time.

Again I hope this makes sense:):)

Thanks for the help guys:):)
 

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dl324

Joined Mar 30, 2015
8,950
So I was just wondering if there was anyway of keeping the Ohms the same for each switch but light the corresponding LED at the same time.
If you don't care about LED brightness (we still don't know if they're the same color), you can use the same value resistor for each switch/LED combination. If you're only going to close one switch at a time, you could use a single resistor.

Another thing you might try is to use the switches on the inputs to a BCD to seven segment decoder and a seven segment display:
upload_2019-7-8_12-48-27.pngupload_2019-7-8_11-28-42.png
EDIT: corrected the wiring for the control inputs on the decoder. Left the original for reference.

That would let you determine which combination of switches were pressed; but it only works up to the number 9. For all 16 combinations, you'd need a hexadecimal decoder and those seem rare these days.

I recently wired a hex decoder with a hex switch and an Arduino Uno to decode the display:
upload_2019-7-8_11-36-28.png
I used inverted logic for the inputs because Arduino has internal pull-ups, but not pull-downs.
 
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ebeowulf17

Joined Aug 12, 2014
2,942
Thanks DL324:):)

This was my original circuit. I was just playing around and wanted to see the ohms that each switch would display. (Please see the attachment)

I then got to thinking, I wonder if I can keep this circuit and use a visual aid to help me see what switch was pressed without using the multimeter. Of course it wont tell me the ohms but It could tell me which switch was pressed. So I attached some LEDs and when I started pressing switches, the LEDs were very inconsistent. Some would dimly light, some switches would allow all to light.

So I was just wondering if there was anyway of keeping the Ohms the same for each switch but light the corresponding LED at the same time.

Again I hope this makes sense:):)

Thanks for the help guys:):)
If you want something like your switched resistor circuit to also have indicator lights, double pole switches (dpst, dpdt, etc) would make it really easy.

Failing that, transistors or comparators could be added to detect the state changes with minimal impact on resistance readings... but it's probably better to wait until you're more comfortable with basics before trying that idea.
 

Thread Starter

beeson76

Joined Apr 19, 2010
193
Wow!! Thanks DL324 and Narkeleptk for the replies:):)

Eventually I wanna get it imported to either the Arduino and/or Raspberry Pi but for right now Im just taking baby steps. I wanna understand this concept before I get into the really complicated stuff:):)
 

narkeleptk

Joined Mar 11, 2019
373
I'm like the blind leading the blind but I think the very basic idea of what you wanted to do would be more like this. Minus the zeners. Not sure if it actually works or not.

11.jpg
 
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Thread Starter

beeson76

Joined Apr 19, 2010
193
Thanks again Ebeowulf17 and Narkelptk for the replies:):) @ebeowulf17 how would I incorporate the DPDP switches. And Transistors would definitely be an option even though I haven't really messed around with them yet:):)

@narkeleptk What do the TP1...TP6 correspond with? :):)

Thanks Guys very much:):)
Mike
 

narkeleptk

Joined Mar 11, 2019
373
TP = Test point. Your description sounded like you where using a dmm to check the different voltages so I figured I would add it in.
 

dl324

Joined Mar 30, 2015
8,950
Eventually I wanna get it imported to either the Arduino and/or Raspberry Pi
I find it cumbersome to have to level shift 3.3V signals from RPi to something more useful. Arduino Uno I/O's are 5V and they'll sink/source 20mA (with exceptions).

I only recently started using RPi because my ARM based SBC of choice is no longer available. Then I ordered an Arduino Uno to find out what all this Arduino stuff was about. Arduino has it's advantages and disadvantages. I consider it another tool in my tool box.
 

ebeowulf17

Joined Aug 12, 2014
2,942
Here are two examples using spdt (single pole, double throw) switches so that each switch movement does two things - bypass resistors and turn on an LED.

It's worth noting that your original schematic shows no voltage source, and it looks like you're using the meter to directly read the resistances. Your later schematics show a battery where the meter measurements were being taken previously. With a battery there, you can't take meaningful resistance readings anymore. Also, reading voltage there will show the same battery voltage no matter what. If you measure voltage at other nodes (as suggested by the test points in an earlier post) then you'll see the voltages change in interesting ways as a result of switch changes.

This version is the closest to adapting your battery powered idea with double pole switches:
upload_2019-7-8_15-56-45.png

Here's a modified version which powers the LEDs, but doesn't power the line of resistors. This way you can still read resistance values directly across the test points at top and bottom (or any other nodes you want in between, assuming they're accessible.)

upload_2019-7-8_16-3-17.png
 

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Thread Starter

beeson76

Joined Apr 19, 2010
193
Thanks Guys:):)

This is awesome!!! Works perfectly. I am able to get my reading for my resistance and a visual aid too.

Thanks Ebeowulf17 and Narkelptk for the help. Much appreciated:):) Now I wonder if I can use a transistor:):) I will look into that do some reading up on it:):)
 
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