Fan for HDD - Page 1
Forum section: electronics / projects

author: kcs
author_rank: Regular Contributor
timestamp: June 29, 2016, 12:32:44 pm
content: I would like to install a fan in my HDD enclosure. There are mounting holes left and I have a fan that fits perfectly (12V, 0.04A), so I don't need to worry about the mechanical part. Question is how to properly connect that fan? HDD enclosure has a LucidPORT USB300 controller that supposed to have an automatic fan control. I would love to find out which pin is responsible for controlling a fan and how it works, but unfortunately I cannot find a datasheet for it. If I have to do it the hard way, I need to find out when HDD is powered on and is not in spin down state. How can I do that?Front of PCB:https://snag.gy/gO0MCj.jpgBack of PCB:https://snag.gy/jzsoeu.jpg

author: ebclr
author_rank: Super Contributor
timestamp: June 29, 2016, 12:49:29 pm
content: If you ac adapter is 12V is theree the point you need to connect your fan ( on the connector pin J3 )

author: kcs
author_rank: Regular Contributor
timestamp: June 29, 2016, 01:05:26 pm
content: Adapter output is 12Vdc, but connecting fan directly to J3 would make no sense at it would be spinning regardless of whether HDD is on or off.

author: Jeroen3
author_rank: Super Contributor
timestamp: June 29, 2016, 01:17:50 pm
content: There are several unpopulated parts. Even a hotglued 4-pin connector, and a bunch of components without obvious purpose near it.There is also a connector left of the hotglued one, which is unpopulated.You'll need to perform a bit of reverse engineering to determine where and what voltage go to the connectors to find out if one is a fan header.Possible even check for EN pins on the smps IC's that disable during sleep. You can use the voltage rail as power switch for an N-fet in that case.

author: kcs
author_rank: Regular Contributor
timestamp: June 29, 2016, 05:48:53 pm
content: 4-pin connector is used to connect soft on/off button and indicator LED, unpopulated connector on the left is actually on/off switch, some models use hard on/off switch instead of soft. There is also J5, it is a GND and another pin connected to 4-pin IC, which I cannot identify (marked as D4DR). It looks like one pin of that 4-pin IC is directly connected to the controller. When I power on HDD, I get 3V3 on J5, when power off - 0V, however, I am still getting 3V3 when disk is spun down. Hence, I believe there is no unpopulated connector for fan control. I can either find appropriate pin on the controller or do some other "magic".

author: kcs
author_rank: Regular Contributor
timestamp: June 29, 2016, 07:16:16 pm
content: I did some further investigation. SMPS near the power jack is MP2365, it outputs 5V constantly (from the moment 12V is supplied, i. e. EN is always high). The smaller SMPS on the back of PCB (marked as IC5AD) supplies 3V3 always when HDD is powered on, even when it is spun down.

author: kcs
author_rank: Regular Contributor
timestamp: July 01, 2016, 08:24:25 am
content: Does anyone have any other suggestions?

author: Powermax
author_rank: Regular Contributor
timestamp: July 02, 2016, 01:06:53 am
content: I assume this is part of a NAS, which has a motherboard already, right? It should already have 0.1 inch pin headers on it for that.There are several ways to control a fan. The most obvious way is to make the fan run all the time with a power supply. It is simple but of course unessesary and loud. If you can use the 12V supply on the PSW (molex connectors), then the fan will turn off when the computer turns off.If you do not have pins on the mobo already, then you could build a linear control circuit which has a temperature sensor and uses a pass transistor to control the voltage across / current through the fan to control the speed. However with only a 2 pin fan we are a bit limited. If the fan is stopped, it needs an initial boost to get going. As a result, Linear control is a bit limited, and inefficient due to it's nature. The transistor so it may need a small heatsink if the fan is large or current hungry.3 pin fans have a tachometer to track the speed of the fan, which allows better control and more reliable operation The Tach will return pulses at the frequency of the fan rotating which a microcontroller or other circuit can track. This allows reliable operation at lower speeds. However this is still limited to linear operation, or low frequency PWM (efficient but more noisy), or LC filtered high frequency PWM (efficient but $$$ because you effectively made a buck converter from scratch) Operating with PWM screws with the tachometer output. One method around this is to occasionally give a long pulse to get a good sample from the tach.4 pin fans, often called PWM fans allow you to control the actual fan itself separately from the tachometer circuit. For these you can apply a constant 12V to the power pins, use the feedback tach pin as part of a control circuit, and the control circuit can modulate the speed of the fan with PWM applied to the last (4th pin). This allows you to just use any frequency PWM by itself without problems. I recommend something like 30 KHz which is low enough to be easy and efficient while high enough to not squeal.