Looking for a 250vAC Mains > OFF timer circuit

[Charlie+]

I have a coffee machine which cooks its gaskets if it is left connected
(easily done) it has high temp protection but this just cycles and and
destroys the machine eventually. The circuit would therefor need to
cope with say 3Kw (250v AC) and any startup surge on top.
Such a circuit would be useful for electric heaters also.

Requirement would be if possible the simplest circuit:
Push button to pass through the mains for a rough set time, about 30
minutes in this case would be most useful . Then remain off until the
button is pressed for another timing cycle. So the timing part could
just be R-C etc..
I dont know enough to design but I can build things! Is such a circuit
even possible cheaply? I can see that even a small ineffiency in
passthrough for so much power would be a problem, so maybe this is pie
in the sky ! Had a good look online and couldnt find such a circuit.
Lots of low voltage/low power examples. Once into relays etc, thats
expensive for such wattage probably. Maybe its cheaper to buy a new
machine occasionally, but wasteful.
Thanks

 

[Lasse Langwadt Christensen]

Den mandag den 21. oktober 2013 09.05.50 UTC+2 skrev Charlie+:

I have a coffee machine which cooks its gaskets if it is left connected

(easily done) it has high temp protection but this just cycles and and

destroys the machine eventually. The circuit would therefor need to

cope with say 3Kw (250v AC) and any startup surge on top.

Such a circuit would be useful for electric heaters also.



Requirement would be if possible the simplest circuit:

Push button to pass through the mains for a rough set time, about 30

minutes in this case would be most useful . Then remain off until the

button is pressed for another timing cycle. So the timing part could

just be R-C etc..

I dont know enough to design but I can build things! Is such a circuit

even possible cheaply? I can see that even a small ineffiency in

passthrough for so much power would be a problem, so maybe this is pie

in the sky ! Had a good look online and couldnt find such a circuit.

Lots of low voltage/low power examples. Once into relays etc, thats

expensive for such wattage probably. Maybe its cheaper to buy a new

machine occasionally, but wasteful.

Thanks

3kw that's a big coffee machine

when I was at universitty we had to have timers on coffee machines
don't remember any names but it was just a plug in timer, so it could
be set to only be on at certain times and it had a manual 1 hour override

-Lasse

 

[Anthony Stewart]

Timers are free add-on now with $1 embedded uC on Smart Coffee makers.

To add one to a not-so-smart coffee maker does not seem worth the trouble with the retrofit involved. The CMOS 4060 clock counter chip could be used with appropriate reset input and timer period output for interfacing to a 15A Triac or Relay with suitable DC power avail.

 

[Syd Rumpo]

I have a coffee machine which cooks its gaskets if it is left connected
(easily done) it has high temp protection but this just cycles and and
destroys the machine eventually. The circuit would therefor need to
cope with say 3Kw (250v AC) and any startup surge on top.
Such a circuit would be useful for electric heaters also.

Requirement would be if possible the simplest circuit:
Push button to pass through the mains for a rough set time, about 30
minutes in this case would be most useful . Then remain off until the
button is pressed for another timing cycle. So the timing part could
just be R-C etc..
I dont know enough to design but I can build things! Is such a circuit
even possible cheaply? I can see that even a small ineffiency in
passthrough for so much power would be a problem, so maybe this is pie
in the sky ! Had a good look online and couldnt find such a circuit.
Lots of low voltage/low power examples. Once into relays etc, thats
expensive for such wattage probably. Maybe its cheaper to buy a new
machine occasionally, but wasteful.
Thanks

http://www.belkin.com/conserve/socket/

Doubt it would do 3kW, but it could switch a relay or contactor.

Cheers

 

[[email protected]]

I have a coffee machine which cooks its gaskets if it is left
connected (easily done) it has high temp protection but this just
cycles and and destroys the machine eventually.

Are you sure all of the temperature limit switches are working? I
wouldn't expect a normally operating machine to cook itself like that.

At a previous job, the safety people insisted that the soldering irons
had to shut off after a while. For the older irons that didn't do this
automatically, we got switches that consisted of spring-wound timers in
an enclosure with a line cord and a socket. The soldering iron power
supply plugged into the switch, and the switch plugged into the wall.
These were designed to cope with US-standard 120 V, 15 A (1.8 kW) loads,
but I am sure something similar is available for 240 V land.

It's also pretty easy (here) to get spring-wound timers that are
designed to install in a standard wall switch box, for running vent
fans, heat lamps, etc. These have maximum on-times of anywhere from
30 minutes to 12 hours. Put one in a box with an outlet, cord, and
a plug to make your own.

The circuit would therefor need to cope with say 3Kw (250v AC) and any
startup surge on top.

http://www.wickes.co.uk/invt/195057 might do what you want, if
"countdown" means what you hope it does. You wouldn't use the "turn
on at 7 AM every day" function; you'd just use the "run for 30 minutes
and shut off" countdown function.

http://www.amazon.co.uk/ANSMANN-AES-1-Energy-Saving-Timer/dp/B005C9S0I8
or http://www.amazon.co.uk/Energenie-Minute-Down-Timer-Plug/dp/B003QPCH2A
will definitely do what you want, and have a simpler user interface too
(one button).

Standard disclaimers apply: I don't get money or other consideration
from any companies mentioned.

Matt Roberds

 

[P E Schoen]

"Charlie+" wrote in message

I have a coffee machine which cooks its gaskets if it is left connected
(easily done) it has high temp protection but this just cycles and and
destroys the machine eventually. The circuit would therefor need to
cope with say 3Kw (250v AC) and any startup surge on top.
Such a circuit would be useful for electric heaters also.

Requirement would be if possible the simplest circuit:
Push button to pass through the mains for a rough set time, about 30
minutes in this case would be most useful . Then remain off until the
button is pressed for another timing cycle. So the timing part could
just be R-C etc..
I dont know enough to design but I can build things! Is such a circuit
even possible cheaply? I can see that even a small ineffiency in
passthrough for so much power would be a problem, so maybe this is pie
in the sky ! Had a good look online and couldnt find such a circuit.
Lots of low voltage/low power examples. Once into relays etc, thats
expensive for such wattage probably. Maybe its cheaper to buy a new
machine occasionally, but wasteful.
Thanks

Reminds me of the time my friend set up a coffee pot at work as he usually
did the night before, which turned on and perked the next morning on a
timer, but forgot it was the Friday before a three day holiday weekend. So
on Saturday it perked and sat there hot for a few hours and turned itself
off, then repeated it on Sunday and Monday and on Tuesday when the crew came
in. There was one guy who really liked strong coffee, and when he got his
big cuppa he remarked that "this is the best coffee you have ever made"!

I have a fairly simple little circuit that fits in an octal relay can, and
is designed to operate as a voltage sensing relay for 80-250 VAC, but it
uses a PIC so it can do a lot of other things too, such as a delayed
turn-off timer. It has a DPDT relay which can handle 250 VAC and 8 amps,
with breaking capacity of 2000 VA, and it's only about $3. You could power
the relay and the coffee pot through both contacts for 16A capacity, and it
could shut itself off after 30 minutes or whatever time you wish. By using a
NO pushbutton across the contacts it will latch on but then need another
push to start up again. The parts for this are just $10-$20, and can be
built on a perfboard. I enjoy programming PICs, but YMMV.

Video:

A really easy and cheap way to do this is a microwave oven timer (or kitchen
timer). Older microwaves had a spring-loaded clockwork dial you could crank
to 30 minutes or so and it can handle a 1000W microwave so maybe also a 3 kW
coffee pot. And BTW that sounds like a really big pot!

Paul

 

[[email protected]]

I have a fairly simple little circuit that fits in an octal relay can, and
is designed to operate as a voltage sensing relay for 80-250 VAC, but it
uses a PIC so it can do a lot of other things too, such as a delayed
turn-off timer. It has a DPDT relay which can handle 250 VAC and 8 amps,
with breaking capacity of 2000 VA, and it's only about $3. You could power
the relay and the coffee pot through both contacts for 16A capacity, and it
could shut itself off after 30 minutes or whatever time you wish. By using a
NO pushbutton across the contacts it will latch on but then need another
push to start up again. The parts for this are just $10-$20, and can be
built on a perfboard. I enjoy programming PICs, but YMMV.

I also have a toaster with broken timer; so, i am in the process of building an add-on timer. I would probably use a 5V AVR, since my 5V/20mA,220V/10A relay won't work with 3.3V. My PICs are 3.3V only.

It will have some buttons and LEDs (any combination can be on):

1. 1 hour delay
2. 2 hours delay
3. 10 hours delay
4. 1 minute cooking
5. 2 minute cooking
6. 5 minute cooking
7. 10 minute cooking

Still thinking if i need a GO button or not.

 

[[email protected]]

On Monday, October 21, 2013 3:05:50 AM UTC-4, Charlie+ wrote:

Yank the over-temperature cutout and replace it with one that has 10oC lower setpoint, this will double the life of the gaskets.

 

[Joerg]

I have a coffee machine which cooks its gaskets if it is left connected
(easily done) it has high temp protection but this just cycles and and
destroys the machine eventually. The circuit would therefor need to
cope with say 3Kw (250v AC) and any startup surge on top.
Such a circuit would be useful for electric heaters also.

Requirement would be if possible the simplest circuit:
Push button to pass through the mains for a rough set time, about 30
minutes in this case would be most useful . Then remain off until the
button is pressed for another timing cycle. So the timing part could
just be R-C etc..
I dont know enough to design but I can build things! Is such a circuit
even possible cheaply? I can see that even a small ineffiency in
passthrough for so much power would be a problem, so maybe this is pie
in the sky ! Had a good look online and couldnt find such a circuit.
Lots of low voltage/low power examples. Once into relays etc, thats
expensive for such wattage probably. Maybe its cheaper to buy a new
machine occasionally, but wasteful.
Thanks

A bathroom timer plus large contactor should do the job. Bathroom timers
are the ones that are customary so people can let the fan run for a
limited time after a major stinky deposit or after a hot shower.
Hardware stores and Internet places have those, even fancy digital
push-button ones:

http://www.amazon.com/Woods-59007-D...qid=1382383772&sr=8-1&keywords=bathroom+timer

On many of them you can also press a button again for more time before
it lapses.

You need to have 120VAC available (can be a small transformer as well)
and a big enough contactor with 120VAC coil (can be bought at
electrician places in town).

 

[Jasen Betts]

"Charlie+" wrote in message



Reminds me of the time my friend set up a coffee pot at work as he usually
did the night before, which turned on and perked the next morning on a
timer, but forgot it was the Friday before a three day holiday weekend. So
on Saturday it perked and sat there hot for a few hours and turned itself
off, then repeated it on Sunday and Monday and on Tuesday when the crew came
in. There was one guy who really liked strong coffee, and when he got his
big cuppa he remarked that "this is the best coffee you have ever made"!

The LM8560 LED alarm clock chip (which is typical for that application)
will turn the aux output on for 60 minutes if the alarm is not stopped.
so probably three one hour runs, (less 3x warm-up time.)

 

[Jasen Betts]

I also have a toaster with broken timer; so, i am in the process of building an add-on
timer. I would probably use a 5V AVR, since my 5V/20mA,220V/10A relay won't work with
3.3V. My PICs are 3.3V only.

you could use a transistor to drive the relay.

does this toaster use a electromagnet to hold the bread rack down or does
it use an expanding hot wire?

It will have some buttons and LEDs (any combination can be on):

1. 1 hour delay
2. 2 hours delay
3. 10 hours delay
4. 1 minute cooking
5. 2 minute cooking
6. 5 minute cooking
7. 10 minute cooking

led illuminated buttons would look good

what needs 10 minutes toasting?

Still thinking if i need a GO button or not.

probably not, my microwave in simple mode has buttons for 1,2,3,4,5,6 and 1/2 minute

 

[[email protected]]

you could use a transistor to drive the relay.

Then i also need a LDO from 5V, and 3.3V for the PIC. AVR can run from 5V directly.

does this toaster use a electromagnet to hold the bread rack down or does
it use an expanding hot wire?

Sorry, it's a toaster oven, with a door.

led illuminated buttons would look good

what needs 10 minutes toasting?

Frozen breakfast, out of the freezer the night before.

 

[Charlie+]

http://www.amazon.co.uk/Energenie-M...B003QPCH2A/ref=cm_cr_pr_sims_t#productDetails

Brilliant - Just perfectly hits my spec. and all for a few quid!!
By the way the ~3Kw part was not for this particular coffee maker but in
case of wanting to use it for other things eg, heaters...
Thank you John, Matt and to all others for your sensible suggestions.
C+

 

[Charlie+]

snip

A really easy and cheap way to do this is a microwave oven timer (or kitchen
timer). Older microwaves had a spring-loaded clockwork dial you could crank
to 30 minutes or so and it can handle a 1000W microwave so maybe also a 3 kW
coffee pot. And BTW that sounds like a really big pot!

Paul

I like this solution, and a visit to the local dump would probably do
the trick for peanuts! C+