Sort of Electronics but still a major fail - Page 1
Forum section: electronics / general

author: chartle
author_rank: Contributor
timestamp: September 13, 2016, 02:22:26 pm
content: I need an AC 110 fan for a BBQ smoker project. Thinking where can I scavenge a 110 fan and I realized I had an old travel hair dryer in the basement (I left it there after I had to thaw some frozen pipes).Its perfect because its small and it has a removable handle. Also since its a travel dryer it has a 110/220 volt switch. I'm thinking if I need to slow it down I can just switch it to 220, run it on 110 and it should be half the speed right.Ok I open it up and pull out the voltage switch to see how it works. Realize that its a dummy switch. It does absolutely nothing. Unless changing the position of a little piece of plastic somehow makes the electrons flow differently.I attached a pic showing the nothingness. I'm assuming that the dryer just runs at normal speed on one setting and double or half at the other and hoping the user never travels out of their voltage zone and notices the difference.Also anyone out there have any knowledge on how to tune a probably fake Berme REX-C100 PID from Banggood.?

author: tatus1969
author_rank: Super Contributor
timestamp: September 13, 2016, 03:11:27 pm
content: looks like that is only the mechanical part. look inside that small electronics box for the actual switch.

author: chartle
author_rank: Contributor
timestamp: September 13, 2016, 03:21:48 pm
content: Yea thats the main 3 position switch, center OFF, up High and down LOW.I'll have to triple check but the the 110/220 "switch" doesn't seem to have any interaction with the other switch. If you look at the third pic the "switch" rides in that saddle. Its a good 2-3 mm away from the main switch and there is nothing pocking out at it.I'll have to take some better pics.

author: SeanB
author_rank: Super Contributor
timestamp: September 13, 2016, 04:52:40 pm
content: Low a diode is in series with the heater, and the 12V motor ( or around 12-24V in most cases) is supplied with a bridge rectifier off a portion of the heater winding. High the diode is shorted out. Most likely they are relying on the positive temperature coefficient of the nichrome wire to provide the semi constant power output with the varying mains voltage. It likely will not glow very brightly on high speed in 115VAC areas, but will glow red on 220VAC areas, giving roughly the same power output.

author: chartle
author_rank: Contributor
timestamp: September 13, 2016, 06:09:07 pm
content: Quote from: SeanB on September 13, 2016, 04:52:40 pmMakes sense when I hit the "Cool" button on low the fan speeds up, when I hit it on high nothing happens.Question, I only want the fan. Can I remove the heating elements and still have the motor work at any speed?

author: rrinker
author_rank: Super Contributor
timestamp: September 13, 2016, 07:10:05 pm
content: The one hair dryer I took apart eons ago, the motor did not run on 120V, there was some circuitry involved to reduce the voltage. I believe the motor was 12V or so. This one was 120VAC only, it did not operate on 240. I don't recall the exact circuit inside, but there was a heat sinked bridge rectifier (I think). Hmm, now I know where that odd piece in one of my junk drawers came from I wonder if I kept it, or threw it out. If I still have it I will check it out when I get home.Even if the motor does run on full power, I think it's probably unsuitable for use in a smoker. A hair dryer fan is low volume, high velocity and I think you'd more likely want something with a larger volume but low velocity.

author: Zero999
author_rank: Super Contributor
timestamp: September 13, 2016, 07:14:26 pm
content: Quote from: rrinker on September 13, 2016, 07:10:05 pmIn a hair-dryer, the voltage to the motor connected to the rectifier is normally accomplished by a huge series resistor which doubles as a heating element

author: rrinker
author_rank: Super Contributor
timestamp: September 13, 2016, 07:33:19 pm
content: Well there you go. It was over 40 years ago I took this one apart and I haven't bothered with any since, they fail so often, mainly from the user not cleaning off the gunked up hair clogging the intake, that they get tossed.

author: chartle
author_rank: Contributor
timestamp: September 14, 2016, 01:46:47 pm
content: But to get back to the main point of my post. I just find it funny that they felt they needed a fake switch on it to make it a "world" hair dryer.One other point this was not some Dollar store purchase. I would have bought it at either Target or WalMart. They are not Macy's but they usually don't sell fake goods.