Author Topic: Adding LED (or?) to shield fan help  (Read 4727 times)

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Offline W9LRT

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Re: Adding LED (or?) to shield fan help
« Reply #25 on: June 23, 2017, 09:17:30 AM »
On an LED, the cathode is typically the shorter lead.  General rule of thumb is most LED's run on 2 volts.  Series resistors are typically 100 ohms per volt you want to drop.  For instance starting with 12 volts, you want to drop 10 volts (to get to the 2 volt operating level), so 10 x 100 would be 1000.  A 1000 ohm series resistor will get you close.  Adjust that up or down to increase or decrease brightness (within reason or you will toast the LED)


Offline dupreezd

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Re: Adding LED (or?) to shield fan help
« Reply #26 on: June 23, 2017, 09:50:53 AM »
Good rule of thumb by W9LRT.

Quote
Adjust that up or down to increase or decrease brightness (within reason or you will toast the LED)
Also, look up the specs of the fan you want to use and see what the maximum sink current of the tach transistor is. Do not exceed that.
If the max = 10mA (.01A) then R = 10V/.01A = 1K Do not go lower than 1K.
« Last Edit: June 23, 2017, 01:48:09 PM by dupreezd »
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Offline 92merc

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Re: Adding LED (or?) to shield fan help
« Reply #27 on: June 23, 2017, 03:53:18 PM »
Here's a stupid idea.  From the ground can you actually see the fan blades?  Or is the shield in the way?

If you could see the blades, just put some paint streaks on them.  You should see them spin then.
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Offline DanS

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Re: Adding LED (or?) to shield fan help
« Reply #28 on: June 23, 2017, 05:16:20 PM »
Here's a stupid idea.  From the ground can you actually see the fan blades?  Or is the shield in the way?

If you could see the blades, just put some paint streaks on them.  You should see them spin then.

In reply #7 Bashy mentioned "Sadly, not possible to see the fan in a Davis shield".

Offline dupreezd

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Re: Adding LED (or?) to shield fan help
« Reply #29 on: June 23, 2017, 06:41:09 PM »
OK, grabbed a fan when I got home and wired it up with the LED in the tach wire. When I stopped the fan, guess what, the LED was on.  :shock:  I then slowly turn the fan by hand and the LED went off. This happened twice during one revolution of the fan. (On-off-on-off).  #-o Checking the fan specs, I saw that the tach output is a hall effect transistor. This means that when the fan stops with the magnet over the transistor, it is on. (electronic reed switch). This makes sense as the tach output two pulses per revolution

I checked the fan I am currently using and it's tach out is a bit different.  \:D/

Looks like W9LRT missing pulse detector might be the way to go. Let me see if I have a 555 around here somewhere.
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Offline Bashy

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Re: Adding LED (or?) to shield fan help
« Reply #30 on: June 24, 2017, 01:44:18 AM »
With what you said about the fan dupreezd, why would a 555 (had to look that up) be needed if the LED does in fact
turn off (or on) when it comes to a stop? please? I have also looked at the 3 and 4 pin fans online and both the
sense (tacho) and PWM have pulses to them, would the PWM work better then the Tach in this instance?
Kind regards
Bashy

Offline DanS

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Re: Adding LED (or?) to shield fan help
« Reply #31 on: June 24, 2017, 02:26:06 AM »
The 555 timer chip can be setup as a "missing pulse detector" to monitor the tach output of the fan. The fan stops and no more pulses out of it.
 The PWM (Pulse Width Modulation) lead of the fan is an input to it. A throttle so to speak.

Offline Bashy

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Re: Adding LED (or?) to shield fan help
« Reply #32 on: June 24, 2017, 02:29:46 AM »
Ah, ok, so then the 555 will then light the LED
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Bashy

Offline DanS

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Re: Adding LED (or?) to shield fan help
« Reply #33 on: June 24, 2017, 02:34:34 AM »
correct.

Offline Bashy

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Re: Adding LED (or?) to shield fan help
« Reply #34 on: June 24, 2017, 02:43:02 AM »
Ok, thanks, next one is this, would the length of the cable degrade this pulse signal, cable is perhaps 5m
just need to know if it would need to be at the fan end or at the PSU end please?
Kind regards
Bashy

Offline DanS

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Re: Adding LED (or?) to shield fan help
« Reply #35 on: June 24, 2017, 02:56:55 AM »
Down at the power supply end for sure. Just extend the tach wire down from the fan to your 555/led circuit. You would need to use the 12v and ground connections from the same power supply as well.

Offline Bashy

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Re: Adding LED (or?) to shield fan help
« Reply #36 on: June 24, 2017, 03:07:36 AM »
Thanks, this could take a while, i cant even remember what size fan fits the opening, i think it maybe an 80mm.
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Bashy

Offline DanS

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Re: Adding LED (or?) to shield fan help
« Reply #37 on: June 24, 2017, 03:39:12 AM »
Lots of fun. I enjoy projects like that. Just be sure to have all your parts gathered, assembled and tested first before taking your station down to minimize down time.
You can Google "555 as a missing pulse detector" and click on "Images" to get lots of ideas and answers.
I think you mentioned that you're using a computer power supply and if so you may be able to use a standard power cable assembly to cut and splice your new circuit and plug right in.
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Offline dupreezd

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Re: Adding LED (or?) to shield fan help
« Reply #38 on: June 24, 2017, 06:59:54 AM »
Quote
Lots of fun. I enjoy projects like that

Sorry, I could not find a 555 at my house. But looking at the circuit, I am starting to doubt if it will work.

Here is my reasoning:- the fan can stop in any of two positions. If it stops in the 'on' position, the tach output will be low, this will turn on the transistor before the 555, preventing the capacitor to charge. This will put the output (pin 3) of the 555 high.
If the fan stop in the 'off', the tach output will be high, turning off the transistor and the capacitor charge up and pin 3 goes low.
Which is what we have now.

I might be wrong on this  :-)
« Last Edit: June 24, 2017, 07:16:05 AM by dupreezd »
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Offline vreihen

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Re: Adding LED (or?) to shield fan help
« Reply #39 on: June 24, 2017, 07:26:08 AM »
I still think that my idea above for using a cheap automotive tachometer gauge is a viable solution, and as a side benefit you can read the fan's RPM to see if it is slowing down due to impending failure.....
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Offline WeatherHost

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Re: Adding LED (or?) to shield fan help
« Reply #40 on: June 24, 2017, 08:53:29 AM »
^^  True. And since the prospect of bring another wire down the mast to connect the gizmos has already been broached, the gauge could be mounted low, or inside an enclosure.  Power can be supplied at the bottom with only the sensor leads extended.  They come in analog or digital too.


You'd have cost into the fan, PS and meter.
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Offline dupreezd

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Re: Adding LED (or?) to shield fan help
« Reply #41 on: June 24, 2017, 10:55:37 AM »
Got it working.

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With the fan spinning, both led's are on. With the fan stalled in any position, only one led is on.

Someone, please try this and see if you get the same results  :-)

PS. If this circuit is independently powered and you loose power to the fan or the tach wire gets disconnected L2 will be on and L1 off.
« Last Edit: June 24, 2017, 11:03:25 AM by dupreezd »
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Offline Bashy

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Re: Adding LED (or?) to shield fan help
« Reply #42 on: June 24, 2017, 11:12:47 AM »
Thats great ya got it working and without the 555, i do not really understand
schematics, perhaps a photo would help me too if and when you get chance
Was that with the 3 or 4 wire fan?
Kind regards
Bashy

Offline WeatherHost

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Re: Adding LED (or?) to shield fan help
« Reply #43 on: June 24, 2017, 11:24:30 AM »
That's another reason to use a Tachometer.  Just connect the wires, no schematic or soldering required.

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Offline dupreezd

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Re: Adding LED (or?) to shield fan help
« Reply #44 on: June 24, 2017, 11:30:19 AM »
Quote
That's another reason to use a Tachometer.
WeatherHost, I really like your idea. How cool would it be if you can extend the wires all the way to your 'weather' room.

Bashy, you can use it on a 3 or 4 wire fan. Let me clean up the rats nest a bit so I can take a good picture.
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Offline dupreezd

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Re: Adding LED (or?) to shield fan help
« Reply #45 on: June 24, 2017, 12:05:08 PM »
Here is a picture of how to wire it up. Of course in the final one, the component wires will be cut much shorter to make it neat and small. You can also mount it on a piece of veroboard
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Note- on the diode there is a grey band, that is the cathode. Make sure it goes the way as in the picture.
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« Last Edit: June 24, 2017, 12:08:40 PM by dupreezd »
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Offline Bashy

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Re: Adding LED (or?) to shield fan help
« Reply #46 on: June 24, 2017, 12:57:43 PM »
You sir are a star, i believe i can work with that, thank you, just need to get me self on ebay now :)

Which LED is Which though?
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Bashy

Offline Bashy

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Re: Adding LED (or?) to shield fan help
« Reply #47 on: June 24, 2017, 01:00:39 PM »
PS, blue wire, top right, whats that one for, im assuming the last black is the GND, just wondering why theres 2 blue and black?

Please can you confirm that this pack will do? its says 1k in the description
http://www.ebay.co.uk/itm/300-Pack-10-Each-30-Values-Resistors-Metal-Film-1-4W-1-Kit-Assortment-Mix-/152168084979?hash=item236decb5f3:g:j7kAAOSwdqRXiIqC
« Last Edit: June 24, 2017, 01:07:13 PM by Bashy »
Kind regards
Bashy

Offline dupreezd

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Re: Adding LED (or?) to shield fan help
« Reply #48 on: June 24, 2017, 01:19:49 PM »
Yes, those will do. They are 1%, so 4 bands to read the value. Makes it a bit more difficult to read if you are not used to it.
The 'normal' ones, 2,5,10% only have 3 bands, (number, number, multiplier).
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Offline Bashy

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Re: Adding LED (or?) to shield fan help
« Reply #49 on: June 24, 2017, 01:21:08 PM »
thank you, i will get them :)
Kind regards
Bashy

 

anything