I have a propane heater, the Mr Buddy Little Heater, and I would like to design an automatic on-off system for it that is based on the readings from a DHT11. The idea is so that it can manage the temperature automatically when camping so as to save propane.
I've been stonewalled by how to activate the "ON" button on the propane heater. The two challenges are that the button goes quite deep in (0.8mm) and also it requires quite some force to press. I'd say the force is equivalent to pressing a thumbtack into drywall.
Does anyone have any suggestions as to how I should approach this?
The following images are the heater itself. The red button is the "ON" button and that's what I'm trying to press with a servo.
It looks like You search for a mechanical button presser. Would it be possible to connect wires to the buttons ( start, stopp I guess)? That feels like a more reliable solution then making a mechaniacal adapter that reliably will stay put.
The two challenges are that the button goes quite deep in (0.8mm) and also it requires quite some force to press. I'd say the force is equivalent to pressing a thumbtack into drywall.
That's probably a mechanical piezoelectric spark generator. If so, you'd need to replace it with some kind of electrical spark generator. I've had a barbeque with a spark generator that runs off a AA battery so maybe you can find something like that.
Then I assume there's a gas valve that you also have to turn-on manually? You'd need a solenoid valve to replace that. Or, maybe you can rotate it with a powerful-enough servo or geared DC motor. A servo is probably the "wrong solution" for rotating a valve...
An automatic gas heater has a safety mechanism to shut-off the gas if it's not ignited or if the flame goes out. Does your heater have that?
Older heaters also have a pilot light and a thermocouple sensor that turns-off the gas if neither the pilot or the main heat is on. The gas valve for my (older) heater is pretty simple... There is a thermocouple & solenoid to hold the pilot light on and another solenoid controlled by the thermostat to turn on the main heater jets. But those things are expensive... I've had to replace it and it was about $500 USD! (plus labor).
@DVDdoug
You point out safety. Really important that a situation where gas is comming out and no flame exist is detected and safely handled. Any automatic ignition might fail and then cutting off the gas is more than important.
Maybe further advice should not be given unless the built in safety of the device is proved.
Regarding safety: Should gas be released without a pilot flame, a separate propane alarm will be used.
In addition, the reason why I want to operate everything using the "on" button is because it minimizes propane exposure. The instructions state that a user should press the on button for 30 seconds, then release it. Say a servo activates the on button, but pilot light fails to ignite in these 30 seconds -- what that means is that a small amount of propane is released. I don't believe this is hazardous. If I am wrong, the alarm will sound.
Regarding operation: the Mr Buddy Little Heater is unique in that all steps are activated through this ON button. It starts the pilot light, then when it reaches a sufficient temperature, a thermal-sensitive device will release more propane to heat the heating tile.
Finally, if it's still unsafe, I could leave the heater outside and heat the (very small) camper van through the undercarriage/window/door. Major loss in efficiency, but safer and no potential moisture problems.
Okey, that sounds a little bit better. What happends if the heater doesn't manage to get the pilot light turned on and the button is still pressed? Gas coming out durint the time of button being pressed?
Still I would prefer an electrical interface like 2 relays doing what the buttons are doing. Mounting a mechanical device will not be easy. A micro controller could use a temperature sensor and create an alarm at missed ignition sequence. Creating a safe time limited "button press" is no problem.
One thing you’ve not considered is if you have a fault with the Arduino , it could leave the gas on .
Ok two things - in the UK modifying a gas appliance is illegal , you might have similar laws in your country.
In use an appliance like that , the human seeing with ignition is successful is fundamental to how it works , the user immediately sees if it ignites .
Thirdly ( !) , using open flame heaters in closed areas such as a camper has the danger of CO production. Methane or CO sensors are not first line control devices , they are a back up fault detection system and not a solution to a bad system.
Personally I would say we should resist offering advice on projects that have safety implications.
@hammy
I fully support Your staements. A human eye, and brain, is the ultimate safety.
An Arduino that keeps on initiating a failing ignition would fill the camper with gas, and then….. boom.
The demands on the quality of the code as well as the technical function of the Arduino.... Don't do this with this kind of heater.
