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How can i increase power output for this 12 v temperature controlled thermostat regulator?
Hi im hopeing there sre some electricians out there that can help me with this problem,I have made up a cooling system that involves x 6 60mm fans with LED`s an wanted to have this system working through a thermostat regulator,so i brought one from link 1 below but mine looks slightly different as you will see in the link 2 below.
The problem i have is i have got 12v 1A going into the regulator but im getting alot less come out back out it feels like half that,so im wondering if there is anything i can replace on the board in link 2 below to get the output power to 12v 1A,if anyone can tell me what components i may need to change and where i would be very great full :) ty
LINK 1
http://compare.ebay.co.uk/like/170782710775?var=lv...
LINK 2
Thank you you very much i think i understood all that,i shall buy a transistor and put a heat sink on as i burnt my thumb on it the other day when setting it up lol :)
3 Answers
- Robert JLv 79 years agoFavorite Answer
I've found the board schematic on the Conrad site (Page nine of the foreign instructions in the link).
It's not a very good design - it uses a 741 Op-Amp to drive a darlington transistor in emitter follower mode.
The 741 output voltage can be anything from 2V to 5V less than the output voltage with a 10mA load, and the transistor will lose another volt.
That means the full output may only be 6V...
The current rating seems to be low purely because the power transistor does not have a heatsink.
Swapping the 741 for a 'Rail to rail' output opamp should drastically improve things.
You need one that will handle the 12V supply, so eg. an LT1677 should work.
The output on that is rated to reach about half a volt less than the supply, so you should get around 10.5V to the fans.
If the transistor gets uncomfortably hot, bolt or glue a piece of metal to it to dissipate the heat (but make sure that cannot short to anything else, it will have 12V power on it).
If you can't see the LT1677 at a normal parts supplier, you can buy the IC direct from Linear or request a sample part - see the link on the right (third item below). Make sure you get the 'PDIP' version, assuming it's an 8 pin through-board chip in yours.
Source(s): http://www.produktinfo.conrad.com/datenblaetter/10... http://cds.linear.com/docs/Datasheet/1677fa.pdf http://www.linear.com/product/LT1677 - classicsatLv 79 years ago
The easy answer is to get another controller and split the fans across them. That should be affordable at 7 quid. They are rated at only 500mA.
A harder answer is to build a second drive circuit to drive the fans the controller cannot control itself, or a high current drive transistor and associated components, to control all your loads.
If the controller is just an on-off controller, you can just use a mechanical relay.
- ?Lv 44 years ago
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