May 27, 2003 — by Mike Chin
Fan controllers emerged as a stock item for case modders and PC hardware enthusiasts in the past year. Once an exotic gadget used only by die-hard, control-obsessed overclockers, mutiple-fan controllers are now made by many different well-known brands, and merchandised in clear plastic bubble packaging — a sure sign of its entrance into the mainstream consumer market. It usually consists of controls and a printed circuit board mounted on a front panel that fits into a floppy or CD drive bay. For the silent PC enthusiast, a multi-channel fan controller is a neat, convenient way to tweak the speed of several fans for minimum noise or to push the fan speeds up as needed for special applications, hot weather, or what have you.
PC fan controllers are not quite as ubiquitous as this kind of fan control… yet.
While some controllers provide selectable settings between 2 or more voltages, others provide a continuous range from as low as 0V all the way to almost 12V. It is almost never a full 12V, because most variable voltage controllers have some insertion loss. Powered by the PC power supply’s 12V line, the controller circuit itself draws a bit of juice, which results in at least a 0.5V loss — not at all significant in practice.
The continuously variable controllers obviously provide more flexibility, but the switched devices have the advantage of easily repeatable settings. This is more useful than you might think, as I often find I need only two setting for my fans — either as quiet as possible without overheating, or full blast and the heck with the noise for now while I run _______ — fill in the blank with whatever you do that pushes your system to its limits.
You’d think getting this relatively simple electronic device right would be a cinch in an industry dealing with some of the most sophisticated silicon wizardry. Apparently this is not so. Vantec’s fan controller was reportedly flawed by major audible buzzing when turned down in fan voltage / speed. Doesn’t seem to be much point, does it? Whether the problem in the Vantec has been corrected is not clear. This is something we’ll be listening for as we examine fan controllers: Noise from the controller itself as well as any extraneous from fans that might be attributable to the controller.
Our first fan controller review is an entry from Sunbeam Company of Taiwan. Coming in the next few days is a review of the Zalman Multi-Fan Controller ZM-MFC1.
| Product | SUNBEAM RHEOBUS |
| Manufacturer | Sunbeam Company |
| Supplier | Silicon Valley Compucycle (SVC) |
| Supplier’s price | US$18 |
The LEDs can all light red or blue. But they are very bright. Blindingly bright. You can, however, easily get them to look more like the photo below (in which only the center 2 LEDs are on, by the way). More on this solution below.
The Sunbeam Rheobus is actually a bit of a misnomer. Rheobus refers to a bus (or voltage line) of rheostats, which are a certain type of variable resistor. A rheostat is a passive device, the simplest type of voltage controller available. It has some distinct disadvantages, such as heating up, and not providing the same voltage control range with all fans. The Sunbeam does not actually use rheostats at all. Instead it uses 4 transistors in active electronic circuits to provide more efficient, repeatable fan voltage control.
As you might guess from the photo above, the Sunbeam has 4 independent channels. It is not limited to controlling 4 fans, however. Each voltage channel can be shared via splitters with more than one fan. As the power rating per channel is a generous 20W, this means a combination of fans rated for a total of up to 1.67 Amps can be accommodated on each channel. That’s as long as the total 12V rating of the PC’s power supply is not exceeded. The Sunbeam, like all the active (and passive) fan controllers on the PC market, is powered by the PC’s power supply. For silent PC applications, the Sunbeam power capacity is probably much more than will ever be needed. Most of our fans rarely exceed 0.15A rating.
Another thing you might have guessed from the photos (and reviews at other sites as well as comments in forums) is that the LEDs are very bright. Bright enough to cause ghosting in your vision should you look directly into them for any length of time from any distance up to several feet at least. There is a simple solution. See below.
Manufacturer’s specifications:
- Power : 20 watt per channel
- Input voltage : DC 12V
- Output voltage: 0 ~ 12 V
- Output current: up to 1.67 A
- Dimensions: 148.5x 105x 42 mm
- Weight (Net) : 184
Like most multi-channel fan controllers, the Sunbeam is meant to fit into a CD drive bay. The front consists of a brush aluminum panel with blue graphics. There are 4 knobs about 3/4″ diameter and 5/8″ deep. Each controls one voltage channel. A bright LED indicator lights up when the knob is turned clockwise, which turns a switch on with an audible click, much like a simple transistor radio. The LED starts out red colored but turns blue past a certain point. The knobs have a smooth slightly frictioned feel, quite pleasant to use.
A few more photos:
The brushed aluminum is probably not a bad match for aluminum front bezels, but depending on how picky you are, it may be close enough, or close but not close enough. Those with cases that have doors over the CD drive bays will be pleased to know that, at least on the Antec cases, there is enough clearance for the knobs; the door closes fine.
A thin layer of foam is affixed to the underside of the PCB. It can’t possible have any acoustic damping function. Perhaps it is meant to protect the board?
The photo above shows the view from top: Power from the PSU is obtained via a 4-pin peripheral connector. Note the four 3-pin output connectors for fans with standard motherboard header connectors. This means an adapter or some rewiring is needed if you have fans with 4-pin peripheral type connectors. (Apparently an earlier version used screw set terminals instead of the 3-pin connectors.) The transistors for each of the channels is cooled by a fairly substantial heatsink, as befits the 20W / channel rating.
Simple Fixes for the Bright LEDs
The photo above shows LED details. Their pins actually plug into sockets on the PCB, and are removable. Just press on the bulb from the front and it comes off the little plastic holder in the front panel. The top photo shows the LED removed next to the IDE power plug. If you are electronically savvy, you could replace these LEDs with ones that are not so bright. Or just remove the LEDs altogether, as the controller works fine without them.
You could also do what I did in the photo above: Pull the LED head out of the front panel hole and position it so that its lens is pointing at the inside of the front panel. That’s how the second photo at the beginning of this review showing the more subdued lights was taken. To me, it is much more livable than leaving the LEDs in stock form.
What about Voltage Control!?
Each of the four channels was tried with several different 12VDC fans: Two 80mm Panaflo variants, a high speed 80mm Sanyo-Denki, and a 120mm Antec. All the controls worked and measured very closely to each other. There was no humming or buzzing coming from the controller at any control setting or combination of control settings. No extraneous noises of this kind from any of the fans could be attributed to the controller, either.
As mentioned earlier, each knob actually operates a switch. The off position is at about the 7:30 position. When it is rotated clockwise, it turns on, and the LED for that channel turns on at full brightness, in red. The minimum voltage is 0.2V. No 12V fan will spin at this voltage. At the 12 o’clock position, voltage output remains at just 2V. At 1 o’clock, output is 4V. Between the 1 and 2 o’clock positions is where most 12V fans begin to spin — about 4~6V. Around the 2:30 mark, 7V is reached. This is when the LED turns blue. After this point, voltage rise fairly quickly to a maximum of 11.5V at close to the 6 o’clock mark.
| Knob position | 7:30 | 8:30 | 12 | 1 | 2:30 | 3 | 4:30 | 5:30 |
| Voltage Output | OFF | 0.2V | 2V | 4V | 7V | 9.3V | 11V | 11.5V |
| LED | OFF | RED | RED | RED | BLUE | BLUE | BLUE | BLUE |
The fan voltage control knobs really have a useful range of only about 1/3 of a turn, from 1:30~5:30. The rest of the knob’s rotary range is basically useless, as fans don’t get enough voltage to even turn on.
Analysis
The Sunbeam Rheostat has some very positive qualities:
- Amazingly low price from the sample supplier SVC: The manufacturer’s suggested retail is $30 but SVC sells it for just $18. That’s cheaper per channel than even a Zalman Fanmate 1.
- Full voltage range from 0-11.5V can be seen as a good thing for hardcore tweakers. Some 12V fan actually start at even 4V or less so the extra range could be useful in getting some fans to run really slowly.
- A mere 0.5V loss at full output suggests efficient circuit design and implementation, and the robust 20W per channel rating is an added bonus for running a large complex system with many fans at low speed.
- It makes no noise whatsoever nor cause any extraneous noise in fans at any speeds or combination of settings.
- The front panel is not that bad for an $18 item — aside from the over-bright LED (which can be easily fixed) and somewhat cheesy blue graphics and lettering,
It does have some points against it, too:
- More than half the control knobs’ range is useless, so it can be very touchy to set within the limited useful range.
- There is no scale around the knobs to help a user visually mark positions for repeatability of settings. This would have been a very simple thing to implement. One could use a felt pen, or some other marker, I suppose.
- When an LED is on, it does not mean that the fan is running. The LEDs are turned on or off simply by the setting of each knob, not by whether a fan is running or connected. This, in combination with the low voltage capability, is potentially dangerous. For example:
A control is set so that a fan start up and runs very quietly, at ~6V. The control is accidentally touched and the fan stops running. Because of the low noise level, this change is not noticed — the LED remains on. The user moves away from the computer for a while. Some kind of thermal overload occurs as a result of the stopped fan. The user comes back and begins screaming when he/she realizes the system has been cooked.
One way around this potential problem is to use the controller in the range where the LED turns blue, which is ~7V or higher. When the LED is red, it then becomes immediately noticeable. This is not a bad solution, but not ideal for many people who like to ramp their fans down as low as 5V.
Conclusions
The Sunbeam Rheostat is very good value for a fundamentally sound, high power 4-channel fan controller. Because of the potential to turn fans off without the user being aware, it is not ideal for casual users. Rather, it is more suitable for more obsessive types who will be vigilant about fan settings. I can also see electronically savvy folks using the Sunbeam as the basis for modding or creating their own customized fan controller. Recommended with caution.
Our thanks to Silicon Valley Compucycle for the Sunbeam Rheostat review sample and their kind support.
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Look for the Zalman ZM-MFC1 Multi Fan Speed Controller
review soon in this section.
