DP832 External 120mm Fan - Page 1
Forum section: electronics / projects

author: rounin
author_rank: Regular Contributor
timestamp: February 13, 2019, 05:57:53 am
content: So I got a DP832 and was irritated at the fan noise. Woo, joined the club.I tried to replace the fan with a Noctua NF-A8, which is nice and quiet, but I'm not sure it really can move enough air.StockME80251V1-000U-A993200RPM33.0 dBA69m^3/hr44.8 PaReplacement AttemptNoctua NF-A82200 RPM17.7dBA23.24 Pa55.5m^3/hrThe stock fan will keep the DP832 @ ~70degC with all outputs shorted at 3A, which is what I figured was the worst condition heat production wise (silver lining, it looks like they actually specified a correct fan for the thermal load! yay!). It also took a long time to climb from 65-70. The Noctua fan very quickly (maybe 10 min) jumped to 70degC and didn't look like it was really slowing down. I'd like to match the original thermal specs / not need to derate my usage of the power supply, but also really don't want to program with the thing next to me with the stock fan. The NF-A8 is "fine" at common usage of 5V 100mA, but I'm going to forget and try to use it to find resistance of some contacts (ie, high current into a short) or something one of these days. I'd rather it stay cooler.So I'm a bit worried that the NF-A8 isn't really enough, and I'll kill the DP832 early from heat. I'm wondering if it is a back pressure issue, and I need a higher static pressure fan to suck air from the sides.I've also thought about getting 3 NF-A8s, and using two as inlet fans. Probably need to seal/duct them for it to do much, and given their lack of static pressure I'm not sure how well it would work.So different idea, use a giant high static pressure fan on the outside, with a duct, and run it slower than normal speed and hope it is quieter for a given air flow.OD1232-24HB 120mm fanhttps://www.digikey.com/product-detail/en/OD1232-24HB/1053-1138-ND/2621043104.6Pa201.6m^3/hr120mm - 80mm fan duct adapter, mounted on the outside of the casehttps://www.amazon.com/gp/product/B002C7IQ1O/I should probably do some hand calcs for the nozzle area / back pressure / flow rate to get an idea of what I need. I don't really want this to turn into a software or hw project, but could consider putting some temperature sensors on the main internal heatsinks and doing a little fan controller.Just not sure if a large/high pressure fan will be quiet when run slower than nominal. That OD1232 fan is like 50dB at full speed, but i might be happy at 1/3 capacity, and if noise is also 1/3 it might be quieter than the stock sunon fan for the same flow rate.How crazy does this sound?

author: technix
author_rank: Super Contributor
timestamp: February 13, 2019, 06:06:27 am
content: Alternative idea: use a fan capable of 4500rpm but is PWM controlled, then build a fan controller board with a few temperature sensors (DS18B20 or LM35) scattered about on the heatsinks. The fan controller board has a micro that would monitor temperatures and spin up the fans only when the temperature gets uncomfortable. This way you know your load is getting heavy when the fan starts screaming while when idling the fan barely spins to spare your ears.

author: rounin
author_rank: Regular Contributor
timestamp: February 13, 2019, 06:35:02 am
content: Hmm something likehttps://datasheets.maximintegrated.com/en/ds/MAX6643-MAX6645.pdfcould be used to control the fan without any software, with two remote temperature sensors.https://datasheets.maximintegrated.com/en/ds/MAX31740.pdfis simple too, but only has 1 sensor.

author: technix
author_rank: Super Contributor
timestamp: February 13, 2019, 07:32:47 am
content: Quote from: rounin on February 13, 2019, 06:35:02 amWorks too, same principle.If you want to, you can make use of the over temperature feature, by adding relays to the board that disconnects the channels if it overheats.