# Simple, cheap timer & Amperage control

#### nebeno

Joined Apr 21, 2013
3
All, first post here. I'm working on a fairly simple project (at least on the electronics side). I'm making a coffee roaster with a built in timer that will shut off the heating element when the timer reaches 0. It will also have a temperature control that can be set between about 300f-550f (setting amperage going to nichrome wire).

For the timer, just something mechanical is fine: turn the knob, the unit turns on, when the timer hits 0 it turns off (just like my toaster oven). All I can find at electronics supply stores online are $20-$30! It seems this must be an incredibly simple device. There will be a few amps running through it, to run a heating element. Right now the cheapest option I can figure is buying a regular wall timer off amazon and taking the internal components out of it. Seems odd that that's the cheapest way to go about it though. It does need to be assembled inside the roaster housing itself (as opposed to just plugging the roaster into the wall unit). Maybe I'm not searching for the right thing, it's a Time Delay Relay right?

As for the temperature setting, this will need to adjust the amperage passing through the switch to the heating element (nichrome wire). Same as the timer, a knob to twist to the desired setting would be ideal. Amperage needs to be somewhere between 2 and 6 (depending on what gauge wire I use). I've tried looking around but honestly I'm not even sure what I'm looking for. All my searches bring up welding components or music related items.

Thanks!

#### crutschow

Joined Mar 14, 2008
30,150
Are you planning on manufacturing these in quantity?

#### nebeno

Joined Apr 21, 2013
3
Who knows, maybe eventually. My goal is to make something for myself and some friends to use. If everyone likes it, I've thought about trying to make something I can sell. If I did though, I likely would continue building them myself for awhile (as opposed to large scale manufacturing). The roaster is going to be a countertop sized unit btw.

#### poopscoop

Joined Dec 12, 2012
140
I know next to nothing, however, everything you described is in a toaster oven. Thrift store one and cannibalize it.

To control the heating element you'll probably need a triac and some time to calibrate it for the desired temperatures.

Be very careful hooking things up to the wall, and ground the case.

#### nebeno

Joined Apr 21, 2013
3
Ya, it is very similar, except for likely a small motor to agitate the beans (or else a fan/air pump to push air through and agitate the beans). I'm just surprised with the price and availability of small motors and fans and wiring and everything else I need that a timer costs so much. I'm at $51 for the rest of the parts aside from the timer and amp controller (or whatever that would be called), that includes wood, glass, filters, etc. I can get a wall switch timer for$5 (http://www.amazon.com/Timex-Minute-...&qid=1366596951&sr=1-23&keywords=minute+timer).

And then a wall light dimmer may work for the temperature (amp) control (http://www.amazon.com/Cooper-Wiring...8&qid=1366597095&sr=1-12&keywords=dimmer+knob).

Thoughts?

Also, i've found a number of sites that sell the various parts I need. Any recommendations on where to buy?

#### poopscoop

Joined Dec 12, 2012
140
A toaster oven has a rotary timer and a temperature controller (Thermostat.)

If you use a traic (Amp controller) it probably will not work without using a lot more electronics. The goal is not to control the amount of current going through the nichrome, but rather to turn it on and off when the temperature inside exceeds the set range.

What you want is a thermostat.