Household oven?

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Household oven?

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Motorious	Motorious posted 9 Years Ago HOT Topic Details
Group: Forum Members Posts: 11, Visits: 99	I did a quick search on this but couldn't find an answer so here is a new topic! Can a household oven be used for curing? Other than a vacuum bag port of some sort, what modifications absolutely need to be made for it to work? I have access to a cheap used one that i could put in my garage but wont bother if it wont work well for composites!
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morepower	morepower posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 242, Visits: 1.2K	You also need to think about how fast it would heat up.. You do need a controlled ramp rate if you only have a simple PID controller. Some may not agree but I have seen a massive difference in finish with a higher ramp rate than the 1 degree every 90 seconds I currently run. I have also seen issues with a temp difference as little as 5 degrees too.. So make sure you check the oven has even heat in multiple locations through the oven and no hot or cold spots. A higher rate of flow from the fan would help if the air flow is not great. My oven recirculates the air once every 12 seconds according to the claimed airflow on the fan. This creates enough turbulence to make the oven have a more even temp throughout.
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Motorious	Motorious posted 9 Years Ago HOT Post Details
Group: Forum Members Posts: 11, Visits: 99	morepower (01/07/2016) You also need to think about how fast it would heat up.. You do need a controlled ramp rate if you only have a simple PID controller. Some may not agree but I have seen a massive difference in finish with a higher ramp rate than the 1 degree every 90 seconds I currently run. I have also seen issues with a temp difference as little as 5 degrees too.. So make sure you check the oven has even heat in multiple locations through the oven and no hot or cold spots. A higher rate of flow from the fan would help if the air flow is not great. My oven recirculates the air once every 12 seconds according to the claimed airflow on the fan. This creates enough turbulence to make the oven have a more even temp throughout. On the subject of controlled ramp rate... I got the SSR and TA4-SNR PID wired and I was messing around with the settings and have realized that I cant control ramp rate with this setup. I can adjust the proportional band which does cause the output to the ssr to cycle on/off but only when it gets reasonably close to the setpoint. if it is say 50 degrees away from the setpoint or more, I haven't figured out a way to change the duty cycle (I dont have an oscilloscope, im just looking at an LED). I am guessing I should have bought a different PID but I'm cheap and went with the $25 one. To get around this and still use the cheapo PID, I was thinking of adding an external circuit inside the box that would intercept the on/off voltage coming from the PID. Then, when the PID is trying to go full blast with a constant 12V out, the auxiliary circuit would turn the signal into a PWM signal that I could control with say a simple potentiometer. Being a non-electrical engineer, I am not sure what would happen to the PID's ability to autotune or what the effect would be when the oven gets close to the setpoint and the pid starts cycling. I was thinking of trying it using a 555 timer based circuit like this one: DIY PWM I have also seen SSR's that are made to have a potentiometer attached and that sounds like it might also work...
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