Hello,
I want to control a 230 V, 100 mA ventilation fan with a regulator. It has to be a digital regulator though that I can control through a MySQL database in the long end..... I obviously don't want a relay because that's on and off. So would I need some type of transistor?? FET maybe?
If so, any suggestions?
Thanks,
Dane
bumpy
well, ac fans are kinda tricky. if its an induction motor you would need a VFD (variable frequency drive) which is expensive and overkill. does the fan need to stay stock? can you replace it with a DC muffin fan? any more information would help.
Yeah it pretty much needs to stay stock.... Yeah I think I'm going to have to regulate AC. I'll try to get a product page..
AC switching with TRIAC from TTL
From: weissj@psd.gs.com (Jeffrey Weiss)
http://www.ee.washington.edu/circuit_archive/circuits/F_ASCII_Schem_PC.html#ASCIISCHEMPC_002
Here's a TRIAC-based solid-state relay circuit:
+5VDC
| 180 180 2.2k
+---/\/\/\----+-----+ +----/\/\/-+--/\/\/\---+-------> 120V
| 1| |6 | | Hot
| +=====+ | | MT1
| | MC | TRIAC | +-+
| | 3032| Driver | G | | TRIAC
| +=====+ | /| |
\ 2| |4 | / +-+
2N3904 |----+ | | | | MT2
/ | +--------- | -------+ |
V \ | | |
| / | \ |
| \ 43 .01u --- 10k / |
| / 500V --- \ |
| | | / |
+------+ | | | Neutral
| +--------+--+---o o--> 120V
/ load
>-/\/\--| 2N3904
\
V
|
---
///
Circuit Description
The MC3032 is an optoisolator TRIAC driver. The 180-ohm resistor sets the current for the LED emitter in the optoisolator. Change the value of this resistor - if necessary - to get reasonable current (e.g., 15 mA).
Note that you cannot test this circuit without a load. The TRIAC will not switch unless connected to an AC voltage source, so you can't test it for simple switching w/o applying AC and a load. Note the 500V rating on the .01 cap.
AC Induction Motor Fundamentals , look at the VFD.
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en012135
Many AC exhaust fans are induction based, which MUST be controlled with a VFD, there is not really any other ways to do it.
So when you change the current to the LED in the optoisolator it changes the current to the fan? Otherwise it kind of looks like a normal relay which would achieve the speed "regulation" I want.
Remember it's a 230 V fan which doesn't really matter but whatever...
Thanks for the replies,
Dane
i think what that circuit was for was for sort of a "dimming" circuit. by triggering the triac at different parts of the waveform you can get different average power outputs, which would control the speed (mostly). i think its a dirty way to control motors but it could work.
more explanation here http://www.ubasics.com/adam/electronics/doc/phasecon.shtml
triacs switch much faster than relays.