A powerlevel indicator of sorts...

[ChemMan]

I must say that this is a very nice site you have here. I am currently constructing a fanbus to control a very noisy fan that I am going to place into my computer in the coming months. After much experimenting with different ways of reducing the speed of the fan I have settled on using a linear voltage regulator to adjust the fan speed. It might not be the best solution, but I'm keeping it simple for my first electronics project. But this brings up one problem. It is possible to totally stop the fan using this circuit and not realise it without looking into the case.:cry: What I would like to do is come up with something that takes an input voltage from 0 to 12 volts dc and indicates the current power level on the outside of the case using a LED or something.8) What I was thinking of doing was having the circuit I described output to a seven segment LED digit, with 9 being the highest voltage and 0 being lowest. Digging around the web I found a page with **broken link removed** circuit about halfway down the page. This circuit uses a 555 timer to increment the counter, but in my circuit I need to replace the timer with something that will set the counter according to the voltage input.:shock: That's about where my very basic electronics knowledge ends, so I could use some advice from people who really know what they are talking about(as opposed to me :lol: ). At the same time I really don't want to get into something too complicated or have to program a chip.(I just can't be satisfied) So, with saying that I will also be taking suggestions for an alternate method. Basically all I want the circuit to do is take the same voltage that the fan is getting as an input signal and be able to graphically display it someway. :?: My electronics knowledge consists of a college level phyics 2 class and what little bit I have scraped up so far, so go easy on me terminology wise. With that being said I learn quickly so don't be afraid to try and explain a concept to me.

Thanks for your input.

 

[mattg2k4]

Check out this article. It uses a lm317 regulator and outputs to a single led, the brightness of which will vary as you adjust the fanbus. All you do is take the output from the regulator and attach it to the led with a resistor.

Or look at an lm3915, it's made to drive 10 (or so) leds which will activate at different voltage levels. It's just got a bunch of comparators inside set to go off at different voltage levels. This way would be more complicated, but I think it would look much cooler, and give you a more precise indication of the voltage. You can run it in dot or bargraph mode. You could also use this to drive a 7 segment led display if run in dot mode.

 

[Mosfet]

The counter circuit counts pulses,
it might be difficult to make a meaningful display.
The barograph idea is a good one.
The LM3915 works great as an audio VU type readout
with its logarithmic scale.
For a more linear display of voltage levels you may prefer the LM3914.
**broken link removed**

 

[ChemMan]

Perfect! I knew about that article using the LM317, but I wanted to come up with something cooler. The LM3914 looks great, I'll get one and give it a try. 8)

Thanks a million!

 

[ChemMan]

After looking at the specs it seems as this thing can disappate a little over a watt of power. Will it be necessary to put a heatsink on this thing? It will probably be in very close quarters with the heatsink on the LM317 with little airflow. I'll have a few more questions coming probably.

Thanks