Voltage guage type of circuit

Click For Summary

Discussion Overview

The discussion revolves around creating a graphical display that indicates the output voltage of a generator connected to a windmill gearbox. Participants explore various methods to achieve this without using external power sources, focusing on the challenges posed by low voltage levels from the generator.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant describes the generator's output voltage range from ~100 mV to ~2.8 V and expresses a desire to create a display that activates LEDs at 0.3 V intervals.
  • Another suggests using transistors biased with resistor dividers to control the LEDs, although concerns about the feasibility of this approach at low voltages are raised.
  • Some participants note that red LEDs require at least about 2V to turn on, questioning the viability of using LEDs without external power sources.
  • There are mentions of using a mechanical display, such as a galvanometer, as an alternative to LEDs, though this too is considered challenging at low voltage levels.
  • Suggestions for using a boost converter are made, but doubts are expressed regarding their operation at voltages as low as 0.1V.
  • One participant proposes the possibility of incorporating a small solar panel to provide additional power for the circuit.
  • Concerns are raised about the overall power output of the turbine and whether it can sufficiently power the desired display components.
  • Another participant discusses the potential use of the LM3914 chip for creating a voltage display, contingent on having sufficient power available.
  • One participant mentions negotiating for the use of a Ni-Cad battery to enhance the project’s feasibility.

Areas of Agreement / Disagreement

Participants express a range of ideas and concerns, with no clear consensus on the best approach to take. Multiple competing views on the feasibility of using LEDs, transistors, and mechanical displays are present, indicating that the discussion remains unresolved.

Contextual Notes

Participants highlight limitations related to the low voltage output of the generator and the requirement to avoid external power sources, which complicates the implementation of various proposed solutions.

pmk0024
Messages
5
Reaction score
0
Voltage "guage" type of circuit

Hi all,

I have a windmill gearbox, connected to a generator. At the lowest speed, the generator outputs ~ 100 mV. At the highest practical speed, it generates ~2.8 V.

I'm trying to make a graphical display that is proportional to the output voltage of the generator.

In simpler terms, I have a DC power supply that sweeps from .1 to 2.8 V. I would like the LEDs to turn on at .3 V intervals.

I've racked my brain, my electronics books, etc and am stuck and have turned for help.

I cannot have any external power sources (to power any type of IC). The idea I'm toying with now is Diodes. This seems like a very simple problem, but I am stuck.

I don't need a schematic, just a shove in the right direction. Thanks so much.
 

Attachments

  • LED.PNG
    LED.PNG
    429 bytes · Views: 440
Engineering news on Phys.org


Use a transistor for each LED, biased with resistor dividers so each turns on at the right voltage.

- Warren
 


I figured I'd run into problems due to such low voltage with transistors (I assume you mean BJT's)
 


And, how can I bias a transistor with a another power supply? The point of this circuit is to demonstrate how one can power a circuit with only wind power. No other batteries.
 


pmk0024 said:
Hi all,

I have a windmill gearbox, connected to a generator. At the lowest speed, the generator outputs ~ 100 mV. At the highest practical speed, it generates ~2.8 V.

I'm trying to make a graphical display that is proportional to the output voltage of the generator.

In simpler terms, I have a DC power supply that sweeps from .1 to 2.8 V. I would like the LEDs to turn on at .3 V intervals.

I've racked my brain, my electronics books, etc and am stuck and have turned for help.

I cannot have any external power sources (to power any type of IC). The idea I'm toying with now is Diodes. This seems like a very simple problem, but I am stuck.

I don't need a schematic, just a shove in the right direction. Thanks so much.

Red LEDs take at least about 2V to turn on, so if you can have no external power sources, then you won't be able to do what you want with LEDs. You might be able to do something with a mechanical display, but even that is going to be tough at those voltage levels.
 


Solution: Boost switcher...
 


pmk0024 said:
Solution: Boost switcher...

Maybe from 1.5V up, but probably not practical below 1.0-1.5V.
 


berkeman said:
You might be able to do something with a mechanical display, but even that is going to be tough at those voltage levels.

In the mechanical category, you could use a resistor and a galvanometer, and have the moving needle gauge be your visual indicator. Should work at those low voltages, as long as you made your galvanometer sensitive down at those low levels:

http://en.wikipedia.org/wiki/Galvanometer

.
 


Oh, right! I didn't realize you could use no other power supplies. You might be able to use a switch-mode boost converter, but none of them are going to operate as low as 0.1V.

By the way, how much power does your turbine generate? Each LED will consume something like 10 mW of power.

- Warren
 
  • #10


You might have to change the requirements a bit. Otherwise this project is going nowhere.

Maybe you could include a small solar panel to give some voltage to run an integrated circuit?
A good source of those is the solar powered garden lights you see in hardware stores for about $5 each. They have a solar panel and a NiCd battery in them. Pretty good value.
They must also have a voltage booster to run a white LED from only 1.2 volts.

Anyway, if you can find some power from somewhere, there is a chip called a LM3914 which does pretty much what you want. It is a dot/bar display driver so you can have a moving dot or a rising bar to indicate voltage.
 
  • #11


chroot said:
By the way, how much power does your turbine generate? Each LED will consume something like 10 mW of power.
That was my first thought. Since the voltage is so low, I question whether it could supply enough power for a group of LEDs. You could use a 1ma meter in series with a 3k resistor. That would give you a full scale reading at 3 volts output.
 
  • #12


Working on talking my supervisor into letting me use a Ni-Cad battery, at the least.

Biasing transistors is my best (as far as the project goes) choice, but I like the LM3914 idea.

Mechanical displays aren't really an option, as we are going for "eye-candy" to entice pre-collegiates into pursuing EE...
 

Similar threads

Powering multiple devices in a low-voltage DC circuit
  • · Replies 18 ·
Replies
18
Views
3K
Simulated voltage gain in Multisim differs very much from calculated
  • · Replies 8 ·
Replies
8
Views
2K
Troubleshooting a Boost Circuit: Voltage Rise & Gate Issues
  • · Replies 4 ·
Replies
4
Views
2K
Help me breadboard my circuit
  • · Replies 10 ·
Replies
10
Views
3K
Can RF101 Diodes Be Used in Low-Frequency Recovery Circuits?
  • · Replies 7 ·
Replies
7
Views
2K
High-energy LC oscillatory discharge: what kind of switch?
  • · Replies 19 ·
Replies
19
Views
2K
Sources of voltage ripple in buck converter
  • · Replies 13 ·
Replies
13
Views
4K
Window fan: Bypassing thermostat with a button
  • · Replies 2 ·
Replies
2
Views
2K
Mosfet SSR, flyback shunt/crowbar safety circuit
  • · Replies 1 ·
Replies
1
Views
2K
Induction heater using Bicycle Dynamo Generator @ 24 V 60HZ Supply
  • · Replies 10 ·
Replies
10
Views
3K