Putting together a MAX6655 monitoring setup

[greenman100]

ok, so after seeing MMZ_Timelord's thread, and the lack of activity, I went ahead and ordered the following

2x MAX6655 chips
10 2N3904 transistors (to have some spares, at 8 cents ea)
24 awg shielded teflon silver cable



so now I need some setup thoughts

on the cable:
connect to ground on the chip end, leave unterminated on the transistor end? Is the cable I got from eBay, okay?

on the soldering:
holy crap these things are tiny....where's the cheapest place to get a couple sockets so I can not spend all day trying to solder this?

on the connection to the mobo:
I have a NF7-S, and I have a header for the SMBus....I just need to connect SMCLK and SMdata, right? Do I need the 10k resistors from the SMCLK and SMdata lines to Vcc? Where can I get those connectors that go to the header on the motherboard? (don't know what they're called)

So, I have the following sensors:

2x2.5V
2x3.3V
2x5.0V
2x12.0V
2 onboard temp sensors
4 remote temp sensors

so I was thinking:
vcore
vdimm
3.3v rail
5v rail
12v rail
case ambient
water
rad airflow inlet
PSU
CPU core (will the SOT-23 package fit next to the die? REALLY don't want to try to cut out the on-die sensor from the mobo, as I like the failsafe shutdown

finally, what kind of accuracy do you estimate from this setup?

thanks for the time

[starbuck3733t]

Accuracy of the 1668 (which I have played with extensively) is about +/- 1*C.

http://smt-adapter.com/perl/site.pl/...apters-QSO.htm
should have the adapter you need. the 6655 is a QSOP package. Keep in mind you now only have to solder to the adapter, and the adapter comes with pre-tinned pads. So long as you get it lined up correctly, soldering the QSOP is not really that difficult. They've done the hard part and gotten just the right amount of solder on the pads of the adapter. My method is to align the chip and tack one corner (1 leg), and then move to the opposite corner and make any adjustments and tack it. Then just go down the line and hit each of the other legs with your needle tip iron for a second or two. CLEAN THE IRON IN BETWEEN TACKS! You do not want to build a solder bridge on these things, they're a ($)##()#$( bitch to get undone (trust me, I've done it!)

Cable looks good, I'm assuming you'll solder it directly to the board.

Not all your sensors need to be the 2N3904 in the SOT-23 package. In my setup I've used TO-92 packaged 2N3904s, much easier to solder. Didn't need the small package because I've sanded down the plastic of the 3904 to be a lot smaller, and I'm not trying to fit anything under a die (can't, have P4!)

your choice of monitoring points look excellent. Don't forget about VGPU-core and VGPU-ram if you've got a fancy voltmodded video card

[greenman100]

$8 a adapter and I still have to solder! I'm thinkng about taking my chances soldering directly to the QSOP!

Don't have a v-modded card, good idea though.

any thoughts on monitoring a 7-29v source with one of these chips?

[starbuck3733t]

No idea about monitoring something 12V+... what is it? Pelt PSU?

The key with hand soldering qsop is to pre-tin the pads in the manor i mentioned. if you're going to try to solder small wires directly to the legs of the chip: let me advise you against that, heartily. The adapter is worth it if you're going to make a 1-off device.

I could put down a 1668 (QSOP) onto the tinned pads on the boards I made in about 20 minutes/chip (including testing)... doing the wires by hand took me close to 4 hours. 3 housr and 40 minutes is worth $8 to me

[greenman100]

a blower PSU.

4 hours! wow.

I'm thinking about bending every other pin upwards, to make it easier to solder. I'll see what I can do...I really want to get this going, and not wait on another part!

[greenman100]

bent every other pin upwards, and got 4 pins done in 10 minutes, but my hands are tired...will resume later.

[Groth]

Originally Posted by greenman100

any thoughts on monitoring a 7-29v source with one of these chips?

Use a voltage divider: two resistors in series from your 7-29v source to ground, then have your chip measure the voltage between the two resistors.

[DrMemory]

Yes you do need the 10K pull up resistors.

Connectors for the SMBus pins can be found at www.jameco.com . They are called .100" non-polarized connector housings and crimp pins (WHEW!), part number 163686CL for the 5 pin housing ($0.27 ea.), and 100765CL for the female "pins" ($0.11 ea.). The minimum order is 10 for both parts. The connectors and pins are sold seperately so be sure to order both. The pins are crimp on but since I don't have a crimp tool for these pins I just strip about 3/32" of insulation off the wire and solder them where the crimp part of the pin is. The wire can be held in place for soldering by using the normal wire anchors on the end of the pins bent around an insulated part of the wire with needle nose pliers. It also helps a lot to pre-tin (apply a small amount of solder) to the wire before you solder it to the pin. The final step is to bend in slightly the crimp parts of the pin with needle nose pliers so they will fit in the connector housing better.

[greenman100]

thanks for the SMBus pins.....and voltage divider help. no sockets for the QSOP, though? besides solder-on...

[Groth]

Too damn small and fragile for mechanical solutions--QSOP means soldering.