Pump for a water-bearing stove

Rolf Guest #7209791
Rate this post
• ▲ useful
▼ not useful 
I have written a program for the Raspberry Pi to control a pump for a 
water-bearing stove. The program works fine - but I still need a 
computer independent safety device. If the Raspberry fails - then it 
must be ensured that the pump runs in continuous operation to avoid 
overheating of the boiler. My first approach was - to evaluate a clock 
signal to be output from the Raspberry. As long as the clock signal 
comes from the Raspberry - as long as a retriggerable monostable toggle 
stage is reset again and again. If the clock signal is missing - the 
pump goes into continuous operation. But if the clock signal remains 
HIGH - then this idea does not work. One must also evaluate the falling 
edge of the clock signal and connect it with logic. At the moment I am 
on the hose - can someone help me?
Reply Quote Edit Move Thread sperren Anmeldepflicht aktivieren Anpinnen Delete topic Thread mit anderem zusammenführen Report post
minifloat Guest #7209916
Rate this post
• ▲ useful
▼ not useful 
Hi,

I suggest to address the problems from the root, in following 
priorities:

1 put an overpressure blowoff valve at the output of the boiler. This 
acts against the fault effect and prevents severe injuries, as the 
boiler tank cannot explode anymore.


2 put an overtemperature switch in series to the heater element. 
Consider also using a non-resettable type. This acts against the root 
cause and also prevents fire.


3 now it is time to think about the additional safety device you're 
planning. Simple solution is make the toggling signal AC by adding a 
capacitor in series and a resistor after the cap to GND. Then feed this 
into the input of a retriggerable monoflop. A simple form of this is the 
attached circuit. (from 
https://cpldcpu.wordpress.com/2021/02/27/the-transistorpixel/ )
Higher capacitor values have to be used, and a resistor in series to 
Q7:collector of a few hundred Ω is advisable.

br, mf
Attached files:
Reply Quote Edit Delete Report post
Watch this topic

Reply

Note: the original post is older than 6 months. Please don't ask any new questions in this thread, but start a new one.

Formatting
  • [c]C-Code[/c]
  • [code]code in other languages, ASCII drawings[/code]
  • [math]formula (LaTeX syntax)[/math]
  • [[Title]] – link to an article
  • Link to another post: right-click its post ID (#8078628), copy the address, paste it into the text

More about formatting

Post long source code as an attachment, not in the text.

Your name and e-mail address

Already registered? Log in

Not shown to anyone. We send you a link; your post appears once you confirm it there.

By submitting you create a free account and accept the terms of use.