NMB Minebea fan - how to regulate speed...? - Page 1
Forum section: electronics / projects

author: gronn-overledning
author_rank: Contributor
timestamp: July 12, 2024, 10:08:17 pm
content: Possible to regulate speed of this fan?Is there some way to regulate speed of this fan?All I need is something lower than full speed, and maybe 2-3 lower speedsA)The easiest for me is to make some arrangement with resistors (I have some high-power resistors, like 5 og 10 Ohms.....25 or 50 Watt).B)Can two fans be connected in serial?C)Eventually use some elecronics...PWM ??I have too little experience with modern modern "shelf-electronics", so I guess I will get quicker answer here...Thanks in advance, for help.NMB Minebea Model 5915PC-23T-B30 techical specshttps://www.allaboutcircuits.com/electronic-components/datasheet/5915PC-23T-B30-A00--NMB/

author: Circlotron
author_rank: Super Contributor
timestamp: July 12, 2024, 10:20:32 pm
content: I have had good results with fans like that by putting about 2 to 4uF capacitor in series with the motor. For best safety should be a 250VAC X2 capacitor. X2 means it is rated for direct connection across the mains, although that is not happening here. Caps will get an easy life because they are protected by the motor inductance.Two fans can be connected in series, no problem. Ideally they should be identical fans.

author: mariush
author_rank: Super Contributor
timestamp: July 13, 2024, 01:58:33 am
content: Maybe using a triac with an optocoupler with zero crossing detection to turn on and off the fan for periods of time.You could try one of those classic light dimmers that cut the peak AC voltages...Next easiest would probably be to get a toroidal transformer designed for 230v - 230v and unwind the secondary winding to make a bunch of steps ex 155v - 170v - 185v - 200v - 215v - 230v then you could use some mechanical relays to switch between windings.If you don't want to rewind transformers, maybe get 1 transformer that does 230v - 120v and then a one or two transformers that have 2-4 24v/36v/48v secondaries and connect the secondaries in series and switch between taps to get a lower AC voltage.With 35w per fan, you're looking at low currents like 0.1A so the toroidal transformers won't need to be big ...ex16$ for 115/230v to 120v AC 56VA :https://www.digikey.com/en/products/detail/triad-magnetics/FD7-120/487868524$ for 115/230 to 120v AC 100VA :https://www.digikey.com/en/products/detail/triad-magnetics/FD8-120/487869529$ for 100V, 120V, 200V, 240V to Parallel 120V, Series 240V 100VA :https://www.digikey.com/en/products/detail/talema-group-llc/0100MD-1-003/4289485add a second transformer to add to the base 120v AC ... exhttps://www.digikey.com/short/mbr58btvThe first may be enough for two fans in parallel, the 100VA ones should do 3 in parallel.

author: David Hess
author_rank: Super Contributor
timestamp: July 13, 2024, 02:21:15 am
content: Quote from: gronn-overledning on July 12, 2024, 10:08:17 pmThat will work, but a high voltage film capacitor like Circlotron suggests will work better because there will be nothing lost to heat.QuoteYes, but the speeds may be too slow or the fans might not start.QuoteA phase control dimmer will work, but perhaps not very well. A variac will work better.

author: gronn-overledning
author_rank: Contributor
timestamp: July 14, 2024, 10:55:18 am
content: Thanks for advice.Looks like easiest and cheapest trying the capacitor.I have to buy one....or maybe looking through the electronics scap container at work. Lots of electronics thrown away there.Forgot to tell what my project is:I will move heated air from the living room where the heating pump and wood stove (oven) is placed, and move the air somewhere into the the kitchen. Already made the 15 cm hole in the wall....1 year agoI the kitchen there is heating cables in the floor, but I dont use it (Norway is cold and electricity stolen from us...prices went up 3-4 years ago).Both rooms are a bout 35 sq.metres (about 350 sq-feet...each?).So because I will use 1 vent-duct (pipe) about 15 cm (6 inch), I actually need just 1 fan).Will the capacitor "slow" down the current, so higher capacity acting kind of higher resistance - less current?Thanks again.

author: Circlotron
author_rank: Super Contributor
timestamp: July 14, 2024, 11:48:15 am
content: Quote from: gronn-overledning on July 14, 2024, 10:55:18 amAt 50Hz a 1uF capacitor will have an impedance (AC "resistance") of 3183 ohms. Double the capacitance will halve the impedance to 1591 ohms.Not enough capacitance and the motor won't get enough power to run.Too much capacitance and the motor will simply run at full speed.

author: David Hess
author_rank: Super Contributor
timestamp: July 14, 2024, 12:17:55 pm
content: Quote from: gronn-overledning on July 14, 2024, 10:55:18 amIt works the opposite way. Higher capacitance results in lower reactance, so the motor runs faster. The reactance is inversely proportional to the capacitance.Rc = 1 / ( 2 Pi F C )

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 14, 2024, 12:21:07 pm
content: The power saved would be minimal, have you considered adding a filter to add restriction while filtering the air?

author: gronn-overledning
author_rank: Contributor
timestamp: July 14, 2024, 03:12:55 pm
content: Quote from: NiHaoMike on July 14, 2024, 12:21:07 pmI have thought about making a filter-casing (dust collector).Its not about saving energy, but reduce possible fan-noise/motor-noise.Now you made an idea into my head.If I make a filterbox of wood, it will make space for 2 fans side by side.Not made the decision yet, to have the fan blow heated air into the kitchen, or transfer (colder) kitchen-air into the heater-pump area, thus forcing the heated air into to kitchen door....as return-air.I actually dont understand the sentence - "...adding a filter to add restricton, while filtering....".I guessed you meant air-filter/dust filter...?

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 15, 2024, 12:05:18 am
content: Quote from: gronn-overledning on July 14, 2024, 03:12:55 pmAll filters introduce some restriction to the flow. Of all the air filters commonly used in HVAC, only the electrostatic type has negligible restriction. (That kind is also quite expensive and more effective against fine dust than coarse dust.) The kind I have in mind are the cheap washable ones.

author: gronn-overledning
author_rank: Contributor
timestamp: July 30, 2024, 06:50:30 pm
content: Update on my fan-project.Tested with two fans in serialMeasured current = 0,1 A. (One alone should take 0,15 A ?....forgot to measure).Speed with two in series was still too high for what I would like.I had to experiment a little...Found one 3,9 kOhm resistor and inserted in the circuit and measured 0,04 A (after a short minute, it became too hot for holding with hands). I guess the speed to around 10 RPM, well, now I know that...Haven't bought or looked for the capacitor yet.Will do (maybe some hint on exact type/product could be useful).Some photos of making the fan-housing.Becomes rock solid with the 18 or 19 mm plywood I use in the main framing (maybe called "furniture sheets"....grabbing from the bin at work.