On demand 12V fan control
Under therrmistor control. If at power up the DC voltage is too low to start
the fan can you always rely on the fan starting at some point with a slowly increasing voltage or does it depend on the make/design of fan ? |
On demand 12V fan control
On Wed, 28 Mar 2012 15:07:03 +0100, "N_Cook" put
finger to keyboard and composed: Under therrmistor control. If at power up the DC voltage is too low to start the fan can you always rely on the fan starting at some point with a slowly increasing voltage or does it depend on the make/design of fan ? FWIW, here is an article that shows the innards of a typical thermistor controlled CPU fan: http://www.pavouk.org/hw/fan/en_fan4wire.html - Franc Zabkar -- Please remove one 'i' from my address when replying by email. |
On demand 12V fan control
On 3/28/2012 9:07 AM, N_Cook wrote:
Under thermistor control. If at power up the DC voltage is too low to start the fan can you always rely on the fan starting at some point with a slowly increasing voltage or does it depend on the make/design of fan ? Different fans will start at different voltages. Your circuit is NOT a thermistor and a fan in series, right? Mikek |
On demand 12V fan control
"amdx" wrote in message ... On 3/28/2012 9:07 AM, N_Cook wrote: Under thermistor control. If at power up the DC voltage is too low to start the fan can you always rely on the fan starting at some point with a slowly increasing voltage or does it depend on the make/design of fan ? Different fans will start at different voltages. Your circuit is NOT a thermistor and a fan in series, right? Mikek I think the question is will the fan ALWAYS start with a slowly ramping voltage, rather than perhaps sit there in a stalled state. Gareth. |
On demand 12V fan control
"N_Cook" wrote in message ... Under therrmistor control. If at power up the DC voltage is too low to start the fan can you always rely on the fan starting at some point with a slowly increasing voltage or does it depend on the make/design of fan ? Some Studiomaster Powered Mixers used to adopt this method - the fan would sit there shaking like a ****eting dog, often making various squeeks, before finally getting going. It was driven by a TIP32. I have no idea whether they specifically chose a fan that would always start though. Gareth. |
On demand 12V fan control
"Gareth Magennis" Some Studiomaster Powered Mixers used to adopt this method - the fan would sit there shaking like a ****eting dog, often making various squeeks, before finally getting going. It was driven by a TIP32. ** A great many power amplifiers have the same kind of circuit. BLDC fans start reliably when the applied DC voltage is about 33% of ated - no matter how slowly the voltage rises. IOW there is no need for a kick start. .... Phil |
On demand 12V fan control
Gareth Magennis wrote in message
... "amdx" wrote in message ... On 3/28/2012 9:07 AM, N_Cook wrote: Under thermistor control. If at power up the DC voltage is too low to start the fan can you always rely on the fan starting at some point with a slowly increasing voltage or does it depend on the make/design of fan ? Different fans will start at different voltages. Your circuit is NOT a thermistor and a fan in series, right? Mikek I think the question is will the fan ALWAYS start with a slowly ramping voltage, rather than perhaps sit there in a stalled state. Gareth. 3 fans fed from the same varying supply. 2 large , one small, all nominally 12V. The 2 large start with the applied "cold" voltage and eventually the small one starts with warming of the amp . Checked by slowly powering from a bench ps a few tmes . But I randomly picked up another new fan that I had about and once out of 10 or so times it did not start by the time it had reached 12V. I decided as this amp was never used for low power use that I would disable the ramping and set it on maximum drive always, not worth the risk/inconvenience of stressed components/mid-performance chance of a cut out |
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