Rpm monitoring and a rheobus

kid6o6 · Post by **kid6o6** » Wed Sep 08, 2004 9:41 pm

Hi all,

very quick question about rpm monitoring. I have my zalman 7000alcu fan hooked up to my rheobus, obviously this means that i cannot monitor the revs. If i was to splice some wires and hook up the blue one to the mb by it'self would it still monitor or does there have to be some sort of circut there for the fan to register and be monitored. Not sure if it makes any difference but my mb is a p4p800.

Thanks

teejay · Post by **teejay** » Thu Sep 09, 2004 3:01 am

My CoolerMaster Aero7 includes a splitter allowing you to connect the rpm monitoring wire to your mobo and the 2 power lines (12V and gnd) to a molex plug. The Sunbeam Rheobus includes a similar splitter so I would say that this is fairly easy to accomplish. Just be sure to hook up the right wire to the right pin... or am I stating the obvious?

len509 · Post by **len509** » Thu Sep 09, 2004 4:19 am

http://store.yahoo.com/svcompucycle/3pinto4pinad1.html

SVC sells a connector that will let you monitor rpm's. Your motherboard model will matter if you really undervolt your fans. My Abit AN7 would not let me go under a certain CPU RPM without setting off an alarm. So this connector was pretty much useless to me.[/list]

Gholam · Post by **Gholam** » Thu Sep 09, 2004 11:31 am

One wire to the motherboard is enough. I just got a rheobus myself, and simply pulled the RPM sensor wire out of the 3-pin connector and plugged it into an empty connector I pulled off a dead fan, then plugged the connector with power+ground wires into rheobus and connector with RPM sensor wire into motherboard.

kid6o6 · Post by **kid6o6** » Thu Sep 09, 2004 3:02 pm

Gholam wrote:One wire to the motherboard is enough. I just got a rheobus myself, and simply pulled the RPM sensor wire out of the 3-pin connector and plugged it into an empty connector I pulled off a dead fan, then plugged the connector with power+ground wires into rheobus and connector with RPM sensor wire into motherboard.

Thats what i wanted to hear. Much obliged.

Gooserider · Post by **Gooserider** » Tue Sep 14, 2004 2:08 pm

Beware of two 'gotchas' though...
1. If the controller uses PWM, you will get unpredictable and probably innaccurate results as the PWM frequency will make the RPM frequency signal erratic.

2. The RPM monitoring circuit works by referencing the fan ground wire which MUST be connected to ground. Some controllers work by going in between +V and the fan, others work by going in between ground and the fan. Either design will work fine as a fan controller, but only the first method will work for hooking up the RPM sensor. Hooking up an RPM sensor to a floating ground may produce results ranging from inaccurate readings to possible mobo damage. To determine which type of controller you have, either check the MFG docs (which may not say) or connect a voltmeter between the ground (usually black) wire on the fan, and one of the black wires on the mobo PSU connector and watch the voltage as you adjust the speed. If the ground is floating, you will see a voltage reading that changes as you adjust the speed, and you shouldn't attempt to connect the RPM wire. If the voltage reads 0v (or close to it), and stays there regardless of fan speed, then the controller is in the hot lead, and you can hook up the RPM wire.

Gooserider

sthayashi · Post by **sthayashi** » Tue Sep 14, 2004 8:05 pm

Gooserider wrote:2. The RPM monitoring circuit works by referencing the fan ground wire which MUST be connected to ground. Some controllers work by going in between +V and the fan, others work by going in between ground and the fan. Either design will work fine as a fan controller, but only the first method will work for hooking up the RPM sensor. Hooking up an RPM sensor to a floating ground may produce results ranging from inaccurate readings to possible mobo damage. To determine which type of controller you have, either check the MFG docs (which may not say) or connect a voltmeter between the ground (usually black) wire on the fan, and one of the black wires on the mobo PSU connector and watch the voltage as you adjust the speed. If the ground is floating, you will see a voltage reading that changes as you adjust the speed, and you shouldn't attempt to connect the RPM wire. If the voltage reads 0v (or close to it), and stays there regardless of fan speed, then the controller is in the hot lead, and you can hook up the RPM wire.

I could have sworn that RPM output was typically an open-collector design, meaning that it is connected to the 12V via a resistor, not the ground. That said, if you have a voltage controller that operates by "lifting the ground," it's still bad, but more for the same reason that the 7V-mod is bad (and in any case, I don't see how lifting ground on the controller end is ever a good idea).