29-01-2015, 20:31
(29-01-2015, 17:57)hvalentim Wrote: I browsed the forum for info on fan control without luck.
If I understood right (please correct me if I am wrong) fan control works by switching on and off power supplied to a 9V fan flowing/feeded trough the board. Or should the 9V merely act to activate an external switch and the fan must have an autonomous power source?
Hi, hvalentim
If I'm not mistaken, we have already talked on another forum. It's nice to see you here too.
The fan gets power directly from the TX board. The on / off function is driven by a MosFET transistor.
(29-01-2015, 17:57)hvalentim Wrote: Which specifications should this fan meet? I guess in the first scenario fan power will be limited by the capacity of the 78L09 regulator, which should be 100ma?
Couldn't we use a 12v fan instead, as these are more readily available?
This question makes me see that I have an error on the TX v2.50 parts list. It will be corrected righ now.
The voltage regulator used on the TX v2.50 board is a regular 7809 (TO-220) and not a 78L09 (TO-92).
This partially answered your question. The 7809 voltage regulator with an heat sink can easily handle 1A. So using a fan up to 200mA it's absolutely safe, and don't cause a significant power loss (heat) on the regulator.
In my two RS I'm using a small 12V fan. It runs slower at 9V, but the air flow it's enough for the job. An additional benefit is that it also produced less noise.
(29-01-2015, 17:57)hvalentim Wrote: Also, under which circumstances/parameters does the fan switch on? I guess these are not configurable?
And yes, the fan on / off condition, it's user configurable.
You can define an Hi and Low outside temperature threshold combined with a Low wind speed threshold.
According to some studies, a fan in a RS only makes difference, when the wind speed is low.
Regards