glend
07-11-2015, 10:02 AM
Most of the good CPU and PC case fans being used for DSLR Cold Finger and Cooler Box builds are PWM fans (meaning they are designed to run on pulsed power). They typically have a 4-pin connector, originally intended to plug into a CPU board header. The four pins are: Ground, +12V, a Pulse lead and a Tach lead (these are called other things some of the time). You can run your fan flat out at maximum rpm simply by connecting just the ground and +12V leads to your power supply. These fans draw next to no current (my biggest fan uses only 0.1amps) but they are voltage dependent. Some of the best fans are now using three-phase motors, meaning that they run smoother than previous fans which are two-phase.
Controlling fan speed, there are a couple of good reasons you might want to do this: reduce noise, reduce potential for vibration (which may migrate to the sensor if not carefully isolated), and avoid annoying breezes blowing the face or hands of you or others. I have lost track of the number of times people at Bretti have commented on the cool breeze coming off my fan. There is also less need for high fan speeds in winter and so seasonal control is feasible with a controller. Integration of fan speed control with TEC power and temperature setpoint management is a more complicated area and I don't want to get involved in that right now.
Typically, people building DSLR cooling solutions just wire the +12V supply up and run the fans flat out, and that's fine, but if you want fan speed control it gets more complicated. PWM fans (with onboard electroncis) should not be powered through a PWM themselves as this can introduce 'transients' and potentially affect the lifetime of the motor. It is best for these fans to be throttled through the 'Pulse' lead. Here is an article that discusses this, and circuit design (simple) for a fan controller circuit that you can build:
http://www.overclockers.com/pwm-fan-controller/
This article is a good introduction of PWMs and fan speed control.
Now I am not an electronics guru, but Rowland is pretty close (at least in the cooled camera area), and he has looked over the above link and has a few ideas on the subject and how it could be done. Rowland care to comment?
So for people buying fans for their cooling projects, think about whether you want to control fan speed, and how it can be done. Hopefully the link helped.
I will be building a 555 timer circuit for my mono cooled camera fan but it will be a month away at least. In the meantime if anyone spots a simple plug and play cheap small box solution let me know.:thanx:
Controlling fan speed, there are a couple of good reasons you might want to do this: reduce noise, reduce potential for vibration (which may migrate to the sensor if not carefully isolated), and avoid annoying breezes blowing the face or hands of you or others. I have lost track of the number of times people at Bretti have commented on the cool breeze coming off my fan. There is also less need for high fan speeds in winter and so seasonal control is feasible with a controller. Integration of fan speed control with TEC power and temperature setpoint management is a more complicated area and I don't want to get involved in that right now.
Typically, people building DSLR cooling solutions just wire the +12V supply up and run the fans flat out, and that's fine, but if you want fan speed control it gets more complicated. PWM fans (with onboard electroncis) should not be powered through a PWM themselves as this can introduce 'transients' and potentially affect the lifetime of the motor. It is best for these fans to be throttled through the 'Pulse' lead. Here is an article that discusses this, and circuit design (simple) for a fan controller circuit that you can build:
http://www.overclockers.com/pwm-fan-controller/
This article is a good introduction of PWMs and fan speed control.
Now I am not an electronics guru, but Rowland is pretty close (at least in the cooled camera area), and he has looked over the above link and has a few ideas on the subject and how it could be done. Rowland care to comment?
So for people buying fans for their cooling projects, think about whether you want to control fan speed, and how it can be done. Hopefully the link helped.
I will be building a 555 timer circuit for my mono cooled camera fan but it will be a month away at least. In the meantime if anyone spots a simple plug and play cheap small box solution let me know.:thanx: