The simple domestic oven presents particular design challenges for the engineer. No more so when the design has to allow for the individual capabilities of a client who is differently abled.
The latter means that no one solution will fit all – examples of solutions include:
A row of toggle switches plus a push button and tilt switch as inputs and two “phone” vibrators as outputs. The bank of switches comprising a set of two to set “hundreds” and another four to set “tens”. The switches provide tactile feedback of the oven temperature set. The vibrators are positioned one at the left hand end of the control box and one at the right hand end. The button is used to request the present oven temperature – left vibrating means temperature is lower than set, right vibrating means temperature is higher than set – both is just right. The client being deaf and severely visually impaired.
Rotary encoder plus two sets of large seven-segment displays. The encoder sets the demanded temperature, as indicated on one display. The other display shows actual temperature. The client being visually impaired but able to read large character displays.
Rotary encoder with push button plus speaker. Voice synthesis gives set and actual temperatures, when the button is pushed. The client being severely visually impaired.
Whilst a wired or wireless link between the oven and control interface is possible – some electronics will need to be within the cooker body itself. If only the sensors. So the first step is to work out where to put them, then monitor the temperatures reached at that location, during normal use.
The design has to either handle that environment or modify it – eg by bleeding off some of the forced air stream used to cool the oven doors or add additional cooling.
All this does mean that it’s likely to be a unique combination of oven, controller and MMI solution – which will need to be tested thoroughly before being handed over.
Then the final design has to be soak tested in the worst case environment, to ensure that the customer will be getting a reliable solution.
MaMa T4CE provides a testbed both for developing solutions and for soak testing the prototype. The top oven has been modified by the addition of a PTC temperature probe:
The probe used is one actually used in domestic ovens. It’s used with a simple controller to accurately set the environmental temperature in the top oven – which is then used to soak test the prototype whilst it is controlling the bottom oven. The bottom oven is fitted with both an additional PTC sensor and a stainless steel thermocouple probe – the two types most likely to be used in practical designs.
The testbed provides benefit to both the client and the engineer – who both have an interest in having a solution that has been tested in a realistic environment for an extended period. Plus, when not being used for testing, the bottom oven does a superb job cooking Ivor Dewdney’s pasties – to sustain the engineer in their workshop… Using a second hand dual oven cooker proved a very cost effective solution.