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yup, simple 45 pence NTC thermistor, it has a starting resistance @ say 25c of 330kohm which drops to zero as it gets to maximum temp (in this case 150c). Once I have it dialled in, in theory, if all fans fail or there is some other heat issue (excessive summer air temps etc) this simple little...

Strike that last statement^^ just remembered, I did a 'spider cob' conversion that used just those type of components and it is more than happy effectively cooling 40w cob's. I doubt the extra 10w would severely hinder it.

OK folks, update on thermistor tests, looks like this latest choice may be pretty much on the dot fer specs, got it cobbled onto the h/s on the top directly above the centre cob, cold power was nearly full power @ 285w so my 25c 330kohm choice is within a hairs crack of poific in that respect...

Ok, just took a look at the specs on the cpu coolers, while i'm sure they are a bargain and you may find some use for them someplace, as to cooling 50w cob's?? they look too small from our experience, I would want probably double the amount of cooling they will provide but I would only be...

you are quite right in thinking 50w of consumption cannot convert into greater than that wattage in heat output, indeed quite the opposite if anything other than heat is the 'output' of the device, heat is the inefficiency in this case NOT the work done. This 'heat inefficiency' is the problem...

Sorry to keep correcting you, but heat watts and consumption watts are two separate metrics, they are connected but the efficiency and power input are the primary variables being discussed here and it is over simplistic to say that because a cpu cooler is rated for cpu's of 100w DOES NOT mean it...

Just by way of explaining myself more clearly, the problem as I see it is this; most heatsink material is spec'd at a c/w figure which can be either total c/w OR c/w per kilo or G of h/s, then to add to that we have the 'theoretical maximum' conversion of electrons into photons @ <800lm/w, so...

Have you seen any of my builds yet? as I suggested these things are all but impossible to calculate, so better to take a known good system and alter as few variables as you can meaningfully calculate. In our experiments here the thermal gradient is more or less linear in c/w so if your h/s is at...

Like you, I looked into cpu coolers as it was a subject I was keenly informed of as a pc builder in the past but...... if your 90w cpu actually emitted 90w of heat, there would be no other functionality, heat is the waste by product of switching in cpu's and due to conversion inefficiency in...

Pretty much our experience precisely, long time hps user, looked into m/h, was given a mono red/blue spider cob type light, most part of useless, awful plant health and vigor, converted it to white cob's and its incredible now, all white cob now and starting to garner some interest from our...

Absolutely agree, was simply commenting on using cpu wattages to guide heatsink choice, not good policy. Could leave you with a set of bad concepts of your subject if you upscale beyond standard cpu h/s capability later.

WINNING!!! well...... TOTALFUCKINFAIL! then some headscratching, then a few more bucks, then WINNING! thermistors from mouser arrived yesterday afternoon, DOH! 300ohm!!! coulda sworn i'd triple checked they were 300kohm!!??? fuckit, only 1000x too low a value! another £17 dahn tha drain, ho hum...

Sorry to differ, that is an over simplistic model, a 90w led does not create 90w of heat! indeed, it is a tiny fraction of that or they would only emit infra red light! The numbers for each cob are on the spec sheet but without a degree in thermal management I'm fucked if I can make head or...

Wotcha, the wattage rating of pc cpu heatsinks has NO direct comparison with an LED equivalent, be careful of basic assumptions. The important number there is the c/w number which gives you the thermal permissivity of the material, have you seen my vero 29 big build thread? it might give you...

https://www.google.co.uk/search?q=sundew&safe=off&hl=en&biw=1365&bih=828&site=webhp&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiTm4aT2vXPAhXDJcAKHfyyATMQ_AUIBigB&dpr=0.75 lots of pics!!!

Personally, I'm beginning to suspect weed is actually carnivorous and the primary role of producing copious amounts of fairly strongly acidic sticky goo, in any other plant, is solely to catch and digest bugs to augment meagre soil nutrients. (Google; sundew) anyone ever found a whole dead bug...

Thermistors just arrived from mouser, few days late but I should still have enough time to shoot a 'how to' vid providing my component selection is in value, the availability of many 'through hole' passive electronics are now becoming hard to find or expensive to buy as the electronics industry...

If the order was for anything bigger than the 250w ones they list publicly they may take some weeks to ship as they customise the transformers to order. The >250w normally arrive in about 10 days from order, and yeah, glen is incredibly helpful and diligent too.

Will be testing some 800w drivers that are even cheaper per watt in a few weeks, I will post the results soon as I have any.

Fuck yeah, worked in multi-kilowatt hps grows, never had an hps burn the skin on my eyeballs like high power leds do routinely, used to work with 4kva industrial mig welders and 5kva plasma cutters, they would burn the backs of yer eyes, these burn the skin on the front. Good shades are in order...