Thanks guys, it all slowly starting to click together in my head. I really don't want the full 150watts and thats why I am trying to figure all this out.

Like since87 said, you could simply apply 24 volts, which should be very easy to do, with 2 el cheapo PSUs, since the current draw is quite lower than the PSU's limit.

At exactly 24 volts, the current would be 2.25 amps for a power of 54 Watts.

Hum... maybe you want more. If you added another 5 volts (from a third el cheapo PSU), for 29 volts, you'd have 2.72 amps, for 78.9 Watts.

you could also use 3 cheap power suplies, conect them in series, and have many ranges in voltages, like 36v (12+12+12), 29 (12+12+5), 22 (12+5+5) etc.

BigBen posted a link to an article about this, looks like an alternative, cheap way to achieve what you want.

I personally think 75 watts is too litle, or maybe even 100 is too litle, i would like to see blocks tested with overclocked processors, around 120 watts.

At 36 volts:
V=36
R=10.67
so I = 3.37
so P = 121.3

Exacly, that why i think the 36 volts are good for this testbench.

What do you ppl think? what amount of Load should be tested?

What might be good is test at 2 or 3 different wattages. More the better I would assume. Then you could make a chart and guesstimate where it would be at all wattages. Say like 75watt, 100watt, and 125watt. I don't know though, had a long weekend and a long day today. My mind is in :drool: state at the moment.... :D

Got my thermocoupler/multimeter today. It kinda sucks because it rounds to the nearest whole number. i.e. 35 instead of 35.5 or 37 instead of 36.6. But it is very responsive. Will get a Fluke version one of these months....

Just tested the Ohms on my new multi meter and it says 10.5 on one and 11.1 on the other. So they are close.

Hey jaydee,

Looks like you have it pretty well figured out with all the capable help here... :)

Sorry for the confusion I probably created in my response back to your PM question - you are correct the heaters are approx 10 ohm (not 4 like I was remembering, duh). While I believe the general idea of my explanation was correct the numbers I was using (ie 12 VDC and 6 Amps) were not valid for those heaters.

One of the reasons I'm using two heaters in my simulator is so that I can generate the heat I want (60 to 100+ watts) with lower voltages. I have two different power supplies that I use to power these heaters during testing (depending on heat load required).

Home-made 0-36 VDC, 5 Amp variable PSU

225-watt, 9-15 VDC, 15 Amp www.jameco.com #175257

Jameco, Digikey, and others have some nice 0-30 VDC, 5 Amp variable PSUs, some with digital meters... Jameco #153242, or #175249 (I just happen to have a Jameco catalog in front of me).

Bottom line - as everyone has said, the heaters have a relatively fixed resistance (~10 ohms) so to set a specific heat output you just dial-in the the voltage and let the current follow, until you measure the right volts and amps to get the watts you want!

With two heater cartridges and the PSU set at 19.4 volts...
19.4 VDC x 1.83 A = 34.9 watts x 2 heaters => 69.8 watts

I use to FLUKE 83 DMM to measure volts and amps
Edit: I use two FLUKE 87 III DMM... (old meter was an 83) +/- 0.05% VDC, +/- 0.2% DC Amps

pHaestus: e-mail me if you would like a couple heaters... :)

FWIW these heaters were used in a cryogenic applicator gun to keep the aluminum body warm so it wouldn't freeze up during use. I have a few 36 VDC and 40 VDC heaters left over from previous R&D work.

Good luck jd,

The wattage shouldn't matter; C/W will be pretty constant (delta T will just get smaller as well). DO be aware that a 0.6A variation means your error bars would be pretty big for any power calculations.

Ah heck, if this keeps up, I'll build a testbench too!

Too bad we can't use natural gas as a heat source ;)

the resistance of the heaters will change with their heat
voltage and current must be measured simultaneously (never calculated based on the presumed resistance)

be aware that there is a voltage drop across the shunt when you measure current
- another correction ('meter burden'), but you can measure it

look at the accuracy specs for your meters (and when were they last calibrated ?)
do not assume that what you read is 'true' just because your meter says so

the cumulative uncertainties will hurt your pride

OT but can those be purchased anywhere? I could use one.

Not sure actually. Look up "cartridge heater" on google. I think these 12V ones where special order though. Probably hard to find. I think Robo got them from an auction if I remember right. Quite a few things that use them though. I discoved 3 things in my shop here at work that use them. All AC versions though.

Made a little progress last weekend on the slug.
http://www.customcooledpc.com/diesim/diesim.jpg

Havn't decided if this will be the final version or not. I might startover on the slug....

through bore it (so you can extract the heater),
put a couple of set screws on the backside to push the heater against the riser

and the really difficult part will be lapping it flat
figured out how to do that yet ?

Good idea on the set screws. No, still havn't decided how I am going to get it flat. I can face it with the mill but it isn't smooth enough. I tried handlapping it and got is nice an smooth but abviously not flat as the corners started to round a bit. N8 lives in this area I might try and see if he can lap it with his equipment when/if I decide on a finished version. Also considering just dropping the idea and sending my stuff to ph. I am not so sure I am up to this or really need it for my projects.

I can get a pretty good idea of how the block is working with the thermo coupler attached to the back of the CPU and a half assed flow rate test. I probably "should" leave the real testing up to people that can do it well.

Still debating. I havn't got to much money in this yet, and now is a good time to decide if I want to dump money on something I may or may not be able to do well/right.....

don't you have a big flat surface where you can lay a gritpaper and then move it around on there?
If you press "right" it can't go wrong :)

Jaydee, did you get any further with this project?

I'm especially interested in how you mounted the heater up to the copper block, it's still a little unclear to me.

This is as far as I got:

http://www.customcomp.us/diesim/diesim.jpg

It is a round heater about 2.5" long. Drilled a 1/4" hole and it slides in.

Update on the die sim. I got a new slug prototype made and am using it right now. Thanks to the electrical lesson in this thread (thanks guys) I got one of the watlow heaters Robo gave me installed and working at 71ish watts with two 12V 15A PS's runnign in series. The pic shows it minus the heater cartridge and mounted probes. I got all that covered in electrical tape for a less than halfassed insulation job. I plan to make a final version of it with some mods and insulate it now that I have the stuff to make it work.
Edit: Die area is 100mm sq.
http://forums.procooling.com/vbb/att...achmentid=4467