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enter image description here

schematic

simulate this circuit – Schematic created using CircuitLab

5 LEDS

  • One LED is to remain always on when current is passed through.
  • One LED will turn on when voltage is between 50 to 90 volts.
  • One LED will turn on when voltage is between 90 to 150 volts.
  • One LED will turn on when voltage is between 150 to 280 volts.
  • One LED will turn on when voltage is greater than 280 volts.

What I have in mind is 5 LEDS, 5 Zener diodes for each range and resistors. Could logic gates come in handy?

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    \$\begingroup\$ Welcome to the site. Please realise that this is not a free design house, homework-answering service or an on-line technical encyclopedia, copied out to you on demand. People will help you take the next step if your question shows that you've done as much as you possibly could on your own - which your post doesn't, I'm afraid. Please revise your question showing your work and findings so far, in considerable detail. Again, a warm welcome to the site. \$\endgroup\$ – Oldfart Nov 16 '18 at 9:37
  • \$\begingroup\$ Thank you for the warm welcome. I have hand drawn my design but I don't know how I can upload it? \$\endgroup\$ – M2T156 Nov 16 '18 at 9:40
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    \$\begingroup\$ Welcome to the site. I suggest you edit your question and use the built in schematic editor to draw your schematic. This way people can edit your schematic to show improvements. \$\endgroup\$ – Steve G Nov 16 '18 at 9:44
  • \$\begingroup\$ What is done usually (and is simpler to design) is that several LEDs will be on depending on the input voltage. E.g. for low voltage, only LED1 is on, for <90V, both LED1 and LED2 are on, etc... and for >280V, all LEDs are on. Is this what you want, or do you absolutely need no more than one LED on at a given time? \$\endgroup\$ – dim Nov 16 '18 at 9:54
  • \$\begingroup\$ Ideally I would like 5 LEDS as described but I fully understand your idea. I am open to that suggestion though. I will upload my idea. \$\endgroup\$ – M2T156 Nov 16 '18 at 9:56
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You have 5 LEDs. One will always be on, and the other 4 are to be controlled. Consider getting a quad analog comparator, and use these to trip at 50/90/150/280 volts. Use voltage dividers before the comparators. Have a reference voltage at 2 volts, or 3 volts, or 4 volts (4.096 volts at +-1% should be cheap to buy) into one of the VIn- or Vin+ pin of each comparator.

You'll have a thermometer-code output. Its your task to define the logic behavior and provide high-current drives to the LEDS.

schematic

simulate this circuit – Schematic created using CircuitLab

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  • \$\begingroup\$ Would you mind sketching it because I am having a hard time drawing it on paper? I have one led drawn before a quad analogue comparator \$\endgroup\$ – M2T156 Nov 16 '18 at 10:51
  • \$\begingroup\$ These are for high voltages and not low voltages \$\endgroup\$ – M2T156 Nov 16 '18 at 10:51
  • \$\begingroup\$ Thank you for that I can understand that now better. So does that mean each comparator will have a voltage reading set? So the voltages I have listed? Would the LEDs be placed at the output of each comparator? \$\endgroup\$ – M2T156 Nov 16 '18 at 11:11
  • \$\begingroup\$ Some comparators can directly drive LEDs safely, if a current-limited resistor is in series with the LED. You must decide that. \$\endgroup\$ – analogsystemsrf Nov 17 '18 at 3:13
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This looks like a job for a LM3914, as it integrates many of the required functions. The low input current makes practical a simple voltage divider at the input, and the rest follows as shown on the datasheet here. Separate power is required, as would be the case for any comparator/logic solution, but overall this is far simpler.

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  • \$\begingroup\$ What do you mean seperate power? So adding battery to power the device? What is the simplest desing in your opinion? \$\endgroup\$ – M2T156 Nov 16 '18 at 11:43
  • \$\begingroup\$ You need a DC supply of between 3V and 25V to power the LM3914 and the LEDs - see the data sheet. I would not advise using a battery because of the current drain, but something like a USB charger would be ideal. Note that you can parallel LM3914 outputs so you can make several voltage increments drive one LED, thus if you choose an increment of, say, 48V, you can light separate LEDs for 48 - 96V, 96 - 144V, 144 - 288V , >288V (These are input voltages before the divider!) \$\endgroup\$ – henros Nov 16 '18 at 12:37
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Even the cheapest MCUs have A to D converters and a voltage reference built in, so there's not a lot of external components needed to make up what is essentially a bar graph display.enter image description here

Here's the first one I found on a search, but you can scale this down to what you are looking for. It can be done with an 8 pin package device for this, or even a 6 pin if you're prepared to multiplex the LEDs, and they start at under 50 cents. It'd be a very different project than doing it with discrete comparators, or with a dedicated bar graph driver like the LM3914 - so you need to decide what you aim to learn from doing this.

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  • \$\begingroup\$ Looks very interesting. But I'm just worried that it wouldn't work with high voltages of up to 360v \$\endgroup\$ – M2T156 Nov 16 '18 at 15:04
  • \$\begingroup\$ All the suggested solutions are low voltage operation, so you scale down the input with a divider - just as happens in all multimeters. \$\endgroup\$ – Phil G Nov 16 '18 at 15:06
  • \$\begingroup\$ Perfect. I will post my results and design hopefully by the end of Sunday. \$\endgroup\$ – M2T156 Nov 16 '18 at 15:22

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