Author Topic: Davis debris screen vs. heater  (Read 1827 times)

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Offline miraculon

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Davis debris screen vs. heater
« on: November 17, 2020, 08:57:58 AM »
Overnight we got about a half-inch of snow (1.3cm). I had left the Davis debris screen in the old-style cone (2nd revision with bird-spikes and ribs).

I turned on the gauge heater (my copy of the Davis heater) and didn't see anything being recorded on the gauge after some time had passed.

Checking the inside of the funnel, I was reminded of the old problem where the debris screen was holding the ice/snow above the heated funnel area.

I removed the debris screen and it is now melting as it should. I usually remove this screen for the winter because of this problem, but this snow caught me off-guard.

Greg H.


Blitzortung Stations #706 and #1682
CoCoRaHS: MI-PI-1
CWOP: CW4114 and KE8DAF-13
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Amateur Radio Callsign: KE8DAF

Offline fkapp

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Re: Davis debris screen vs. heater
« Reply #1 on: December 10, 2020, 02:07:02 PM »
What did you use for the transformer on your homemade version of the Davis heater?
I have the Davis heater but when moved somehow the transformer went missing (AC-power adapter part).
Bummed out as can just order up some 20 AWG wire, but need some help with what to order to step down the AC.

Will this work (Plan to plug in GFI outlet in my shed)
https://www.amazon.com/PWS-2420-Supply-Adapter-Transformer-terminals/dp/B06XRJQS25/ref=sr_1_21?dchild=1&keywords=24v+plug+in+transformer&qid=1607628219&sr=8-21

Looking at the manual runs on 24V, 24 Watts at the heating "coil"

Thanks
Frank

Offline miraculon

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Re: Davis debris screen vs. heater
« Reply #2 on: December 10, 2020, 05:07:13 PM »
What did you use for the transformer on your homemade version of the Davis heater?
I have the Davis heater but when moved somehow the transformer went missing (AC-power adapter part).
Bummed out as can just order up some 20 AWG wire, but need some help with what to order to step down the AC.

Will this work (Plan to plug in GFI outlet in my shed)
https://www.amazon.com/PWS-2420-Supply-Adapter-Transformer-terminals/dp/B06XRJQS25/ref=sr_1_21?dchild=1&keywords=24v+plug+in+transformer&qid=1607628219&sr=8-21

Looking at the manual runs on 24V, 24 Watts at the heating "coil"

Thanks
Frank

It shows "24V 20VA Power Supply", VA is basically "Watts" for a resistive load, which is what the heater is.

I found a wire-in 100VA transformer on eBay years ago and it has worked for six winters just fine. As long as the voltage is correct (24/25V), having a higher power capability can't hurt. That 20VA one will probably not deliver the right amount of power to the heater and may fail from being overloaded.

I see a number of 75VA to 100VA transformers on eBay and Amazon. I recommend the higher safety factor so it isn't being overloaded. You might get by with a 50VA transformer, but the higher power ones really not that much more expensive. You might need to do some wiring, though.

I would recommend something larger than 20AWG wire as well. I have successfully used the wired yard light cable for my heater. I think that it is 16 AWG. It can be buried in the dirt as well. (I would try to protect it from shovels, etc. in the future)

Greg H.


Blitzortung Stations #706 and #1682
CoCoRaHS: MI-PI-1
CWOP: CW4114 and KE8DAF-13
WU: KMIROGER7
Amateur Radio Callsign: KE8DAF


Offline miraculon

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Re: Davis debris screen vs. heater
« Reply #4 on: December 11, 2020, 02:41:08 PM »
Thanks for the help. Narrowing down transformer and found this cable. https://www.amazon.com/dp/B06XKTBM1B/ref=cm_sw_r_sms_awdb_imm_t1_tuS0FbMYKTFW8?_encoding=UTF8

I saw that one too. For another $10, you could get Southwire 14/2 low-voltage cable. Depending on your wire run distance, it might help reduce voltage drop.

https://www.amazon.com/Southwire-55213243-Landscape-Lighting-100-Feet/dp/B004YKCBI6

Greg H.


Blitzortung Stations #706 and #1682
CoCoRaHS: MI-PI-1
CWOP: CW4114 and KE8DAF-13
WU: KMIROGER7
Amateur Radio Callsign: KE8DAF

Offline fkapp

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Re: Davis debris screen vs. heater
« Reply #5 on: December 11, 2020, 09:20:44 PM »
Thanks. Is about a 50 ft run so guess is a toss up on which one to use.
I found this transformer that am planning on ordering
https://www.amazon.com/dp/B01N3ALUBS/ref=cm_sw_r_u_apa_fabc_tIc1FbQFDGXRP?_encoding=UTF8&psc=1

Thanks for the help
Frank

Offline miraculon

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Re: Davis debris screen vs. heater
« Reply #6 on: December 12, 2020, 09:08:54 AM »
Thanks. Is about a 50 ft run so guess is a toss up on which one to use.
I found this transformer that am planning on ordering
https://www.amazon.com/dp/B01N3ALUBS/ref=cm_sw_r_u_apa_fabc_tIc1FbQFDGXRP?_encoding=UTF8&psc=1

Thanks for the help
Frank

That xformer ought to work with 2.1A available. I have an AC ammeter on my heater line and it runs just under 1A, so this transformer will work.

My calculations based on a standard resistance table show about 1V total voltage drop for 20AWG, ~0.4V for 16AWG and ~¼V for 14AWG.

This works out to 21W for 20AWG, and only a fraction of a watt delivered to the load difference between the 16AWG and 14AWG (just over 22W for either). The terminations may be easier to handle with the 16AWG. You are right about it being a toss-up. You can go with the 16AWG.

Greg H.
 


« Last Edit: December 12, 2020, 09:11:42 AM by miraculon »


Blitzortung Stations #706 and #1682
CoCoRaHS: MI-PI-1
CWOP: CW4114 and KE8DAF-13
WU: KMIROGER7
Amateur Radio Callsign: KE8DAF

Offline ksmoody

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Re: Davis debris screen vs. heater
« Reply #7 on: February 16, 2021, 07:10:01 PM »
What was the value and wattage of the resistor you used at 24 volts.

Offline davidmc36

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Re: Davis debris screen vs. heater
« Reply #8 on: February 16, 2021, 08:00:59 PM »
I have a butt load of resistors and probably have that covered.

I wonder too about the thermal switch. I can do power and resistance from stock. What switch? How much hysteresis? What value resistor?

Offline miraculon

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Re: Davis debris screen vs. heater
« Reply #9 on: February 17, 2021, 10:19:02 AM »
See this for the bimetal thermostat: https://www.wxforum.net/index.php?topic=27859.msg269235#msg269235

And this for the resistor value and other details: https://www.wxforum.net/index.php?topic=22128.msg212809#msg212809

There are other details in the entire thread.

Here is the BOM (w/2014 prices) of items that I used:

Quote
Vector Board: $13.28 (but I could get many boards from the 12"x12" board)
50W 25 Ohm power resistor: $9.83
Flag terminals (flattened a bit to mount to PCB): $2.99 for more than I needed.
Terminal Block: $2.49
Screws (mix of new and junk drawer): Few bucks.
Bi-metal thermostat: Radio Shack via eBay: $3.89

The resistor can be seen in the photo. It is a large wirewound 50W 25 Ohm. It draws just about an amp off my transformer supply.



Greg H.


Blitzortung Stations #706 and #1682
CoCoRaHS: MI-PI-1
CWOP: CW4114 and KE8DAF-13
WU: KMIROGER7
Amateur Radio Callsign: KE8DAF

Offline davidmc36

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Re: Davis debris screen vs. heater
« Reply #10 on: February 17, 2021, 03:33:36 PM »
So looking at some Bi-Metal that kicks on at like 3-5C and off at 10 or 12?

Offline miraculon

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Re: Davis debris screen vs. heater
« Reply #11 on: February 17, 2021, 04:30:07 PM »
So looking at some Bi-Metal that kicks on at like 3-5C and off at 10 or 12?

Davis web site for the gauge heater has:

Quote
When turned on, the themostat switch turns power off if temperature reaches 110°F (43°C), and turns it back on with temperature drops to about 85°F (30°C).

The 104°F one was the closest that I could find. I had to really search to find the correct temperature for the bi-metal, and I couldn't find an exact match.

Greg H.







Blitzortung Stations #706 and #1682
CoCoRaHS: MI-PI-1
CWOP: CW4114 and KE8DAF-13
WU: KMIROGER7
Amateur Radio Callsign: KE8DAF

Offline davidmc36

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Re: Davis debris screen vs. heater
« Reply #12 on: February 17, 2021, 06:09:44 PM »
OK. Seems pretty warm........hmmmm.

Maybe I will try the gadget I bought extra for.the Grow Tent. Can be programmed for whatever On/Off points you want. Stick the probe under cone and it can turn a 12V "Wall Wart" on and off.

Will only be probe and 12 volts running outside.

I only want to experiment with one of my three cones. It is close enough to back door I think to run the power.

Offline miraculon

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Re: Davis debris screen vs. heater
« Reply #13 on: February 18, 2021, 10:21:30 AM »
I have an Ambient Weather temperature probe stuck inside the Davis rain gauge housing. During the recent cold snap, it was struggling to maintain temperatures in the 40°F range (~5°C) when it was windy with single digits ambient.

During milder weather, I can see the temperature cycling due to the thermostat. The bi-metal is close to the power resistor and runs hotter than the interior sensor temp.

I used to have a 60°F bi-metal before I bought the 104°F one. I don't recall exactly what the issue was, but I deemed it as giving unsatisfactory results.

The heater has its "pros and cons". It tends to completely evaporate light fluffy snow and will not record anything even if there is a few inches.

It does solve my pet peeve of indicated precip counts when it has been dry and sunny for days and the snow starts melting out...

There is a plot generated by meteobridge PRO from this probe on my rain page.

Greg H.



Greg H.


Blitzortung Stations #706 and #1682
CoCoRaHS: MI-PI-1
CWOP: CW4114 and KE8DAF-13
WU: KMIROGER7
Amateur Radio Callsign: KE8DAF

Offline davidmc36

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Re: Davis debris screen vs. heater
« Reply #14 on: February 18, 2021, 03:10:35 PM »
Thanks for sharing the details. I am getting a better understanding of what goes on under the hood.

I probably won't get around to building in the remaining winter this season.....project for next fall lol.