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Just pondering over the idea of fitting a small (60-80mm) case fan to my mirror.

The 'scope I am using doesn't have a plate covering the back of the mirror so any fan would have to attached directly, maybe stuck on with sticky foam pads?

It'd have to be fairly slim to fit in the gap between the mirror and the floor for transporting, as I usually stand it on it's end .

I'd like to know what I should use to power the fan. I do not have a powertank to use so I am assuming batteries are the only option. In that case what connections/wiring are needed to make it work?



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Thanks Shane for the link :o

I found my thumb screws which I used to my own collimation knobs and they fit perfectly. This means I can use them to mount a disk with a fan attached.

Just need to ask a few more questions:

*What material can the mounting disk be made of, cardboard, plywood?

*I have no access to mains when observing, how would I wire up a battery/s to power the fan?

*Would this fan be suitable? 3 PIN 60 12V case Fan Coller Cooling XKS6015h12S for PC on eBay (end time 05-Oct-10 13:15:53 BST)

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excellent Tom - how lucky was that (I mean skillful :o )

I don't think it matters what the disk is made of but something not affected by damp would be good and relatively easy to cut. I think I have even seen cardboard covered in black insulation tape.

re wiring batteries up I am not 100% sure but I bet if you went to Maplins or similar they'd be able to help. I know they have to be run in sequence whatever that means! again I'd be interested to see what you do (pics please!!) as I will be going remote someday too.

the size of the fan would be fine although I tend to go for two wire ones as I am never sure what the yellow one is for!

let us know how you get on. I have just fitted a small fan to my 6" dob which went OK.

I may have to fit a slightly bigger one though. - trialling at the minute. see toward the end of http://stargazerslounge.com/diy-astronomer/115026-ongoing-mods-my-orion-optics-uk-6-f11-planetary-dobsonian.html

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I have a 200p dob and I've justed added a fan having pooled the tips from a few of these threads. I'll post some pics when I can work out how to do that but it's not as smart as some of the diy jobs I've seen by Russ and Moonshane etc...

I bought an 8cm quiet computer case fan from ebuyer.com, a zultan fan controller and a battery pack (for 8 AA batteries = 12V) from Maplins. I then cut a doughnut of wood (from the base of a old drawer) 22cm outer 8cm inner. Then fan attached to the doughnut with a few pins and the doughnut to the ota with sticky back Velcro. The fan blows against the mirror and fits on the outer side of the doughnut. A bit of wire stripping and joining connects the battery pack to the controller and then the controller to the fan. Wiring instructions How to Wire a Computer Fan | eHow.co.uk

I'm a total diy novice and I certainly need to tidy up my joins with soldering and tubing but it currently all is working nicely.

You could Velcro the fan to the doughnut and screw to the base using the three free holes in the bottom of the ota and M3 screws as other diyers seem to have done.

Good luck


Edited by Skills
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nice one Adrian

order of priority for mods:

1) does it work?

2) what does it cost?

3) does it look pretty?

the other two over-rule the last one :) which comes with time and level of fussiness! :headbang:

start a new thread or add some pics here if Tom's OK with that - we always like to see mods as they often give us ideas!

how good are dobs for fiddling!? :o

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Ok now I seem to be getting a general idea of how it all goes together. I just need to know how to connect the battery holder to the fan speed controller cable. The page states that the connector is PP3???


These are the components I was looking at getting for this project.


60mm Internal Cooling Fan In Black - 4pin Molex.. | Ebuyer.com

Speed controller:

Zalman Fan Mate 2 Speed Controller : Cooling Accessories : Maplin

Battery holder:

AA Size Battery Holders : Battery Boxes : Maplin

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Zalman, yeah that's it.

Pp3 clip: PP3 Type Battery Snap : Battery Clips : Maplin

(the guy in the shop put one in my hand :o )

So the pp3 clip runs off the battery pack giving you 2 bare wires red and black. The controller (and fan) has 3 wires and ends in a clip of some form. Cut out the redundant yellow wire and join the other two wires matching the colours - the link I gave above gives all the information you need, the fan controller just sits in the middle but it doesn't alter the wiring (3 wires in and out).

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ive just added a cooling fan to my 200mm reflector,didnt want to cut a hole in the backplate so i made my own i use perspex which has ali skins on both sides,i got it from a sign maker i know,its light and easy to cut,was white so painted it black,when mounting the fan i used an old mouse mat cut to the right shape to try to cut down on vibration(not sure if it works yet clouds clouds and more clouds lol).I also drilled three 8mm hole so i could adjust the mirror without having to remove the plate.Just need a clear night now to try it.





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Ok that's the stuff ordered. The three electronic bits from maplins plus this fan from Amazon. 80mm might be a little oversized but it'll do for now. £1.85 with free p&p direct from Amazon :o

I think that until I have the perspex stuff from stanlee, I will improvise and use a piece of card with a hole in it.

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Thank you Stanlee, I have PMd you :o

The parts from Maplins have arrived, the battery box, pp3 clip and fan speed controller. I am now just waiting on the arrival of the actual fan from Amazon, dispatched today via super saver delivery.

I can see there is a fair bit of wiring to be done when all the bits arrive. The fan has a 4 pin molex connector and the fan speed output only has 3 so I'll have to strip the the connectors off and wire them directly. Same thing to be done with the pp3 and the fan speed wire. I don't have a soldering iron so I'll have to make do with stripping the insulation off and twisting the bare ends together and then shielding with electrical tape.

Edited by Hypernova
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Got your address now will try and post in the next day or 2.Good luck with the mod let me know how you get on with it.When i asked if 10" x 10" was ok is only 9.5" x 12" just checked on my 200 reflector and it should be ok just.

Edited by stanlee31
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Thanks Stanlee, I received the perspex this morning :(

I will get round to cutting it out later on in next week but in the meantime I'll get all the electronics sorted, all of which have now arrived.

So to sum up; I have a battery box with a pp3 clip, fan speed controller with two separate connectors which do not fit the fan and a an 80mm fan with two 4 pin connectors.

I need to know now if I am to still ignore and get rid of the yellow and wires connected to the fan and the speed controller? According to the eHow link they are for computer control of the fan and I don't know if they are necessary to manual control of the fan's speed. Also the fan has two connectors which are bridged by four wire. I don't know whether to cut the fan's wire above the connectors and connect directly to the fan speed wires or not?

Same sort of confusion with the white wire on the fan speed side, I don't know if it is needed or not?

I am also assuming that the set of wires with the yellow wire is the output to the fan and the one with white wire are for the input from the batteries.

Pictures attached of what I'm working with here.



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hi Tom

the red on the fan and the red on the battery pack (also of course black/black) certainly go together. if you cut off the connectors as these are not needed. solder the bits together (or use a connector block) and this will work on it's own (although with 4aas you'll only have 6v so the fan will run at half speed at most).

not sure about the controller but I'd connect the red/red and black/black and see how you go. I don't think you'd need the other wires. if using a connection block then terminate the yellow and whites in separate sections of this so you'd have a four connection block with red/black/white and yellow on one side and just red and black on the other - not sure what you need to do if these connections don't work. I personally just use a mains variable voltage transformer at home and have just today rigged a battery version like yours for in the field - I hoped one of mine would work with 4.5v (off the battery) but alas not. it does though work off 4.5v on the transformer so not sure why. will need to investigate.

Edited by Moonshane
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