home improvement turns into science fair projects?

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JR.
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Re: home improvement turns into science fair projects?

Post by JR. » Wed Jun 17, 2020 8:05 am

I couple weeks ago I sprayed my (tent) caterpillar killer... a bacteria that selectively kills caterpillars. It works.

I don't know how much the tent caterpillars effect yield but I prefer not seeing them...

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

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Re: home improvement turns into science fair projects?

Post by JR. » Wed Jun 17, 2020 8:24 am

New project, or variation on an ongoing project.

Last year I purchased an inexpensive but obviously over capacity blower to circulate air between my back bedroom and main room that has heat pump temp control.

The blower instructions warn against using a dimmer circuit and I see (hear) why, using a cheap lamp dimmer causes an audible hum... I could repurpose an old variac I have laying around but it is huge and doesn't easily fit. I will keep it in mind as one possibility.

I have experimented successfully with using capacitors in series to drop voltage... two 22uF in series (11uF effective) drops the speed into a usable range, but it would be nice for it to be adjustable.

To fabricate a simple LxC LPF using the 22uF caps I already have requires tens of mH inductors... Digikey wants $50+ for likely suspects. :oops:

I am wondering is I could perhaps use an old fluorescent ballast in series after the dimmer and feeding the 22uF to smooth the voltage feeding the blower?

I vaguely recall upgrading to a modern ballast in my old fluorescent, before I removed them. I don't want an electronic ballast but old school inductor.

Any thoughts?

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

terkio
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Re: home improvement turns into science fair projects?

Post by terkio » Wed Jun 17, 2020 9:25 am

I presume the noise, using a cheap dimmer is because of power is far from sine, made with a triac with delayed conduction.
A PWM technique is prone to make such trouble, too.
I have seen a two speed ceiling fan where a capacitor is inserted to give the slow speed.
This is not continuous as you wish but a proven technique.
What about a compromise.
With more caps and switches you can make several speeds you might be happy with.
These caps ( widely used for starting asynchronous motors ) are easy to source in the values you need.
This can be fun designing binary coded speed steps.

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Re: home improvement turns into science fair projects?

Post by JR. » Wed Jun 17, 2020 10:45 am

terkio wrote:
Wed Jun 17, 2020 9:25 am
I presume the noise, using a cheap dimmer is because of power is far from sine, made with a triac with delayed conduction.
A PWM technique is prone to make such trouble, too.
I have seen a two speed ceiling fan where a capacitor is inserted to give the slow speed.
This is not continuous as you wish but a proven technique.
What about a compromise.
With more caps and switches you can make several speeds you might be happy with.
These caps ( widely used for starting asynchronous motors ) are easy to source in the values you need.
This can be fun designing binary coded speed steps.
I already designed a 2 speed switch (last summer) using an on-off-on switch and 22uF caps to provide a couple speeds and off, but it would be nice to have it continuously variable.

I momentarily thought about chopping the mains voltage at higher frequency to shift the HF content even higher perhaps reducing the 60Hz noise, but too much work.

I had a ceiling heater in the bathroom above where I am mounting the blower and my old school variac might fit inside that old heater back box. I need to measure it. FWIW that (really) old variac hums a little by itself. New variacs cost more than inductor. I could tolerate a little variac hum in the bathroom but not the cheap triac dimmer hum.

I suspect a simple LPF might reduce the noise, I am just not going to spend $50 for an inductor. Since the blower has far more output than needed I could experiment with a RxC filter. I have a few power resistors sitting around and could tolerate some loss.

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

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Re: home improvement turns into science fair projects?

Post by JR. » Wed Jun 17, 2020 11:22 am

another option,,, I stopped using my 2 speed switch last winter, when I fed the blower from my proportionally controlled baseboard heater. I tapped the blower into the middle of two baseboard heaters so their impedance helped filter out noise.. While this was super slick to have the blower follow the thermostat for heating, it doesn't make sense for summer cooling.

The two speed switch is actually off/1 on/both on. Since I now can power the blower from my old bathroom heater wall switch, I can reconfigure my 2 speed switch into a 3 speed switch, and use the wall switch for completely off.

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

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Re: home improvement turns into science fair projects?

Post by JR. » Thu Jun 18, 2020 6:24 pm

I just did a test rewire of my 2-way switch as a 3-way.... 8-) It works like a charm.

High speed is still 1x22uF in series... moving so much air it makes duct noise.. but good for quick air exchange. I'll use this next winter when I close off the back bedrooms with no heat during day time. At night the high speed will be useful to warm up the back room, and full off, for daytime when heat is off.

Medium speed 2x22uF in series, was my recent normal and it moves plenty of air. While not completely silent it is quiet enough to not keep me awake at night.

Low speed 3x22uF in series is even slower and quieter yet... my new night time mode... :D

I need to figure a slick way to mount this switch, need to cut a rectangular hole in a steel box, and squeeze 3 big caps inside the box mounted to the blower for line cord and thermal fuse... I may just hang down the switch on a wire dongle...

But the speed control is sorted... 8-)

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

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Re: home improvement turns into science fair projects?

Post by terkio » Fri Jun 19, 2020 2:54 pm

Excellent.

I presume this speed control has perfect efficiency, no heat from the caps.

3 caps, 2 switches.
I guess you obtain the 3 cap values by shorting some cap(s). Is that ok for a swich when shorting a charged cap ?

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Re: home improvement turns into science fair projects?

Post by JR. » Fri Jun 19, 2020 4:35 pm

terkio wrote:
Fri Jun 19, 2020 2:54 pm
Excellent.

I presume this speed control has perfect efficiency, no heat from the caps.
yup
3 caps, 2 switches.
I rescued the switch from an old carpet cleaner, weird common wiper, 0=both open, 1=1 on, 2= both on. IIRC one switch position was for heater and other for for carpet motor.
I guess you obtain the 3 cap values by shorting some cap(s). Is that ok for a swich when shorting a charged cap ?
I'll find out... this is AC so caps are not charged to DC, or shouldn't be... I was surprised when wiring up the switch to draw a spark from one of the caps.

==

Last night I slept with blower in new super low speed... Sweet, dead quiet. In the morning the temps were well normalized so it doesn't take much air exchange to work. For daytime I have it switched to medium speed,,, high speed is too high for normal use.

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

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Re: home improvement turns into science fair projects?

Post by terkio » Fri Jun 19, 2020 5:56 pm

It takes little fan speed to get good heat exchange.
I had a very noisy PC box. So I invested in a larger CPU fan with a big heat sink and speed controlled by cpu temperature.
Then I found out that most of the noise was from two case fans that were large but running fast blowing a hurricane through the case.
So I simply rewired those fans to run them on 5 volt instead of the 12 volt. Then I only had a gentle breeze to remove eventual hot spots.
I got a damn quiet PC and saw not much heat from the temperature monitoring, even under extensive computing load.

AC caps with a motor on mains power.
I think they get charged and discharged at 60 Hz frequency. So can hold up to 110V sqrt 2 plus or minus DC depending when the gear is switched off.
Forgive me, if I am all wrong.
Or play with your caps to measure what DC can be in when removed.

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Re: home improvement turns into science fair projects?

Post by JR. » Fri Jun 19, 2020 9:09 pm

terkio wrote:
Fri Jun 19, 2020 5:56 pm
It takes little fan speed to get good heat exchange.
yup... one of my patents is for a heat sink design.

I had a very noisy PC box. So I invested in a larger CPU fan with a big heat sink and speed controlled by cpu temperature.
Then I found out that most of the noise was from two case fans that were large but running fast blowing a hurricane through the case.
So I simply rewired those fans to run them on 5 volt instead of the 12 volt. Then I only had a gentle breeze to remove eventual hot spots.
I got a damn quiet PC and saw not much heat from the temperature monitoring, even under extensive computing load.
true
AC caps with a motor on mains power.
I think they get charged and discharged at 60 Hz frequency. So can hold up to 110V sqrt 2 plus or minus DC depending when the gear is switched off.
Forgive me, if I am all wrong.
Or play with your caps to measure what DC can be in when removed.
I have no desire to measure them but 250V, decent film caps so I feel lucky.

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

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