Electronics help needed - Simple timer circuit

valve90210

valve90210

valve90210

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17 Jan 2006
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Can anyone help me either find or create (what I hope will be) a fairly simple timer circuit?

It will probably be helpful to explain what I want to use it for...

I have a bbq fan controller which has a temperature probe and a fan. The temp probe goes in the bbq and when the temperature is below that which is set as the target the controller switches the fan on to blow more air onto the coals and bring the temperature up.

This works quite well with one exception. When you lift the lid to check or wrap the meat etc naturally the temperature drops dramatically. The coals are burning nicely and just enough to give my target temperature and once I close the lid the temperature in the bbq will get back to where it was within a few minutes which is fine. However when using the fan controller, all it sees is the temperature drop and switches the fan on the whole time it's reading a lower temperature than the target. This ends up getting the coals far hotter than they were and the temperature ends up overshooting where I want it.

Where does the timer circuit come in? Well, I would like to be able to create something which can be put between the controller and the fan with a simple push button so before I lift the lid I can press the button and the power to the fan will be cut for a few minutes to give the bbq time to come back up to temperature to hopefully avoid the overshoots.

Is things something that would be simple enough to create?
 
What about a break to break switch

Ie when you lift the lid you break the fan connection, when you reclose the lid it remakes. That way it will reengage once you shut the lid and should quickly blow it back up to temp, but wont engage whilst the lid is open?

I am quite interested in this fan controller though, aiming to get into smoking a bit this year, do you have a linky?
 
555 driving a power or solid state mosfet that the fan runs through should do it should be loads of examples on google or I can probably put one together later.
 
Mercenary Keyboard Warrior said:
What about a break to break switch

Ie when you lift the lid you break the fan connection, when you reclose the lid it remakes. That way it will reengage once you shut the lid and should quickly blow it back up to temp, but wont engage whilst the lid is open?

I am quite interested in this fan controller though, aiming to get into smoking a bit this year, do you have a linky?
Click to expand...

Link for the controller: http://www.allchinas.com/lite/

emjK5cX.jpg


It's quite good though the lid lifting issue is a bit annoying, and it does take a bit of getting used to.

The problem is not the fan running when the lid is off, it's more that the fan runs for a time while the temperature comes back up to the target. The coals are already burning just right for the target temperature and the additional fan blowing gets them too hot and it overshoots the target temperature.


Rroff said:
555 driving a power or solid state mosfet that the fan runs through should do it should be loads of examples on google or I can probably put one together later.
Click to expand...

That's the sort of thing I was thinking about. ideally if the circuit could be powered by the output to the fan from the controller and it just doesn't pass that power on to the fan for a time once the button is pressed would be ideal.

As you can see in the pic above, the flan plugs into the controller, in an ideal world I'd like to add a small box which the fan plugs into and which in turn plugs into the controller so it can be powered by the controller output and pass the power to the fan.
 
Last edited:
If you want to really over-engineer this set-up an Arduino to read the temperature and use a PID controller to regulate the fan/temperature to whatever setting you like. Stick an ESP8266 wifi chip on there and you can have push notifications and monitor/control the thing via your phone remotely :D.



Actually, looks like someones already made an open source Arduino/Raspberry PI BBQ controller, awesome :D:
https://github.com/CapnBry/HeaterMeter/wiki/An-Introduction-to-LinkMeter---HeaterMeter

HeaterMeter is an AVR / Arduino microcontroller-based automatic BBQ controller. Temperature data read from a standard thermistor (ThermoWorks, Maverick) or thermocouple probe is used to adjust the speed of a blower fan motor mounted to the BBQ grill to maintain a specific set temperature point (setpoint). A servo-operated damper may optionally be employed. Additional thermistor probes are used to monitor food and/or ambient temperatures, and these are displayed on a 16x2 LCD attached to the unit. Buttons or serial commands can be used to adjust configuration of the device including adjustment of the setpoint or manually regulating fan speeds.

The HeaterMeter board can optionally be mated to a Raspberry Pi (Model A, A+, B, B+, Zero, Zero W, Pi 2 and Pi 3) to provide web access. Web access provides live streaming updates, graphing, archives, and SMS/Email support for alarm notification. Android and iPhone apps are also available but not required, the website works on mobile devices as well (asterisk: it isn't a mobile site, but it does work).
Click to expand...
 
 
Pho said:
If you want to really over-engineer this set-up an Arduino to read the temperature and use a PID controller to regulate the fan/temperature to whatever setting you like. Stick an ESP8266 wifi chip on there and you can have push notifications and monitor/control the thing via your phone remotely :D.
Click to expand...

Apart from the wifi notification and control part, that is pretty much what the bbq controller I have is, it's a PID controlled unit.


Mercenary Keyboard Warrior said:
Think this may be even better as you can pick the time and fix it
https://www.ebay.co.uk/itm/DC12V-30...575470?hash=item2f0784532e:g:3VUAAOSw2kZZbCLI
Click to expand...

That does seem to be the kind of thing I'm after, I sadly am lacking the electronics knowledge to know how I can make that (or something similar work with the output from the controller that I have...
 
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