I have a chest freezer that I keep in an outbuilding.
On at least one occasion, for whatever reason (lightning?), this freezer has thrown a breaker, cr@pped out (without us knowing it) and stunk up the garage with rotten food and bait.
(We only rarely open the freezer, so it took a while for us to realize that it had thrown a breaker and was powered down.)
Does anyone know of a simple way I could rig something up to show when the freezer stops pulling current for more than, say, a day or two?
At first I was thinking an ammeter would work, but obviously, the freezer isn't running ALL the time, so the lack of current wouldn't necessarily indicate a problem.
What I would like is a prepared solution for this, perhaps a gizmo that would go between the freezer and the 110V outlet that would LIGHT UP or SOUND A SIREN when the freezer stopped drawing current for more than a specified time.
Does anyone know of a device that would work for this purpose, or of a simple way to make one (I can solder, but beyond that, I'm pretty clueless, so be gentle!)?
On a sunny day (Fri, 20 Apr 2007 13:19:47 GMT) it happened Jones wrote in :
Perhaps the simplest (and better) way is use a temperature sensor. You can use a simpel silicon diode, at the input of an opamp, that triggers a beeper for example (via a wire in the house).
I dunno if you can make that, if you think you can I can post a diagram. (run from an AC adapter).
Perhaps complete remote temp sensors exists that have an alarm?
I would not bother measuring current, as that is no indication you did not leave the door open for example. Always measure what you want to know, not some related value.
Make sure the breaker is NOT GCFI. GCFI's are NOT recommended fro freezers, refrigerators, etc.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
America: Land of the Free, Because of the Brave
Some times old fridges have motors, whost startup current peaks a causes the breaker to kick in.
**** Disclaimer *********If you are not experienced in electronics AND electrical safety then do not attempt these suggestions *****
**** Tinkering 240V ac / 110Vac mains voltage can be hazardous to your health! ****
**** If any of this is unfamiliar then seek electrical professional help before attempting any thing *** Now the disclaimer is out of the way.
In stores , most freezers are fitted with over complicated alarms...They have to meet food regulations.
Thermostat's A temp sensor - hooked up outside to detection threshold device or circuit, hooked up to a buzzer.
I remember when I was 10years old (some time ago) there are some temperature switches that you could connect to a battery and a buzzer... depending on your electrical / electronic skill. (backup battery and plug pack used as the power source)
Oh, yeah, I remember now - they are call thermostat's here's the 1st search on google.
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If you are building only a few there will be other places that sell small volumes. Make sure the wires don't cause a poor seal on the door. And there is no mucking around with the Hazardous mains (240/110V ac) voltage.
Parallel Voltage measurement. The mains failure might be a circuit beaker or mains power as you suggested.
This idea is cheeky but effective.... because is also not connecting "directly" with mains high voltage (240V/ 110V) (which is hazardous to your health)
- Put the fridge and a low voltage AC adapter in to the same power board or
2way power board. something like this one (but for your country)
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- Use the output of the AC adapter and connect to the coil terminals of relay (same voltage as the AC adapter's --> DC output)
- Wire the relay's Normally Closed(NC) terminal to the + side of a battery
- Wire the relay Common (C) terminal to a + side of DC buzzer same voltage as the battery
- Wire the -side of the battery to the -side of the DC buzzer.
When the mains power is on the AC adapters DC output keeps the relay contacts open between (C) and (NC), the battery is off, not drawing any current.
When the mains power is off, the relay is de-energised and the (C) and (NC) contacts connect causing the buzzer to go on.
It's cheeky because the when the power is off the buzzer will be on.. so it's a sort of built in backup.
AC Mains Current detection
*** Dangerous unless you know what you are doing *** I can see where you are going buy trying to measure the current, so nothing is connected directly to the fridge.... but it will need battery backup if your whole house/building power fails.
Suffice to say you can use a type of current transformer.... sorry no more details without knowing your electrical safety experience.
Alarms are simple. I also have made alarms with battery backup in case the power is off. Its to warn of meltdown. Most common ones now are batery opperated. there is a device I have seen on the market that I thought was very cheap which monitors AC current but no alarm. Probably usefull for determing startup current. Radio Shack?
You can buy alarms that react to the temperature in the freezer. You could also (instantly) detect the power failure at the outlet, for example with a beeper, battery and a mains voltage AC relay (use a normally closed contact).
But if your freezer is causing the breaker to trip there's something wrong with the freezer and/or the breaker.
Best regards, Spehro Pefhany
--
"it\'s the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
Around other parts, some people will plug in two or three coolers into one breaker. Most of the time two will work OK on a 20 amp breaker, but still risky. Three definately no. Most cruise at 5-8 amps, but at start up can triple or more. Every once in a while they all try to come on at the same time.
I just wish they would put clocks in them fridges and allow one to set the defrost time. I alwas detected when it was after a defrost by how soft the ice cream was. happens with all of them. I measure the temps over several days. After a 45 minuite defroast cycle it gets up to 26 degrees for a short interval. If one opens the door on a hot warm summer day, it goes up######. The refridgerator section actually has better temperatur control, but still if you open the door your in trouble.
The best freezers for long term storage DO NOT have an auto-defrost cycle. That's how you get freezer-burned food.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
America: Land of the Free, Because of the Brave
I have sad experience with that. When we moved, the house came with the existing refrigerator, so we moved it to the garage as a beer cooler and freezer overflow. That garage outlet is on the same circuit as the backyard outdoor outlet, so it is GFCI-protected. My son fooling around with the outdoor outlet (sticking a weedpuller in it) triggered the GFCI circuit. We found out several days later after the frozen fish had thawed.
I contemplated dumping the beer along with the fish, but a few short taste tests proved that it was not completely spoiled.
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