Question about Capacitors which i emailed Dave about - Page 1
Forum section: electronics / projects

author: Zip
author_rank: Newbie
timestamp: November 22, 2019, 12:15:15 pm
content: Hello dave i just watched your video about capacitance multiplier i have a question.Im building a dc power supply and fan cooling unit box for my server rack.6 x fans > I have multiple sized fans and blowers2 x power supplies > one 12V and one 5V PSU(5v railis for two usb power supplies i require)(12v is dedicated for thermostats and fans)3x thermostats > I have three thermostats for three levels of cooling2 x capacitor banksNow i have a question about wiring in my capacitors this is what i want to do tell me if in going down the wrong path.12V PSU wired to capacitors == then capacitors wired to thermostats == then thermostats which have inbuilt relays to turn the fans on and off.I wanted to include capacitors as i have noticed the fans draw power when they all turn on at once but wasnt sure if i should include the capacitors before the thermosats or after or both?Also i would like to work out the ideal sizes capacitors required for this project?

author: excitedbox
author_rank: Regular Contributor
timestamp: November 22, 2019, 03:43:50 pm
content: Not really much information but you put the caps where you need the power. You can consider caps like a power input or small battery. So if you just want to keep even power going to the fans then put them near the fans.

author: Zip
author_rank: Newbie
timestamp: November 22, 2019, 06:29:38 pm
content: Can i use these in parrallel with the fans if the fans are 12V but these caps say 16v or will it offset the psu

author: thm_w
author_rank: Super Contributor
timestamp: November 22, 2019, 11:36:45 pm
content: You can put them in parallel but they may not even be necessary. Have you measured the voltage of the 12V output and tried to turn on all of the fans at once and see what it drops to?If the 12V PSU is adequately rated, I'm thinking it won't be much of an issue.If capacitors were needed, I would put them on the output of the 12V supply, prior to the thermostat, to avoid switching into the capacitor which will cause a large amount of current to flow for a short time.

author: Zip
author_rank: Newbie
timestamp: November 23, 2019, 02:34:35 am
content: When all the fans click on at the same time the temperature leds on the thermostat dim slightly.So it makes sense to put them before the thermostat but i wasnt sure if the electrons would try flow back to the psu this way?Otherwise i can put them after the thermostat relay on the fans 12v rail this way it would charge the capacitor just prior to turning the fans all on?

author: Zip
author_rank: Newbie
timestamp: November 23, 2019, 02:36:02 am
content: And yes the 12v psu has enough amps to run all the fans plus more so just trying to give the thermostat a boost when all fans click on so it doesnt dim the temperature guage leds on the thermostat

author: Zip
author_rank: Newbie
timestamp: November 23, 2019, 02:37:48 am
content: I guess my reply to your above response is if i put caps rated to 16v on a 12v psu will thr psu charge them to 16v or only 12v

author: thm_w
author_rank: Super Contributor
timestamp: November 25, 2019, 10:58:57 pm
content: Quote from: Zip on November 23, 2019, 02:34:35 amDimming sounds like the 12V is dipping quite a bit, measuring it will tell you how much and let you compare before and after adding capacitors.The PSU has capacitors inside already, adding more externally is not generally going to be an issue, nothing will flow back into the psu.Quote from: Zip on November 23, 2019, 02:37:48 am12V