Kitchen Hood

Dear all,

I'm mechanical engineer with poor knowledge on electronics and programming, but i'm really curious about and would like to learn. I have basic knowledge on arduino.

My project, I think very simple for you, is the following:

I have build my house near Paris and i'm finishing the kitchen. One of my friends gave me a kitchen hood, and I opened it to get the motors and fan to make a custom one, integrated in my custom furniture.

The motor has 5 wire : one for the neutral, and 4 for the 4 speeds levels : high / mid-high / mid-low / low. When you connect the 220V to he high speed wire, you get a high aspiration. Quite easy to understand.

I would like to use a push button to control the hood : one push -> Low speed, another push -> medium speed, etc. And why not a long push to turn it off.

My idea is to use 4 electric relays connected on each wire, and make a program on arduino to control each relay depending on number of push from the push button.

Do you think it is a safe way and a good way to make this ?
Do you have better idea, or advice to make it in a safe way ?
which kind of relay should I use, and is there any advice on how to use and mount it ?

Thanks in advance for your feedbacks,

Best regards,

Dimitri

The safety of this project depends on how you implement both the hardware and software. For instance, what experience do you have of electrical installations at mains voltage ?

There are also potential dangers with the software. For instance, is it safe to connect 2 or more of the speed control wires to 220V ? I know that this is not what you are anticipating but you must consider possible failure modes.

The fact that you need to ask about types of relay and how to use them is worrying. My advice would be to experiment with the principles of your project using an Arduino with the switches and LEDs (used to emulate relays) on a breadboard and not to use mains voltage until the software is thoroughly tested.

I would suggest that the actual electrical installation be done by a qualified electrician and that this should include the supply and fitting of relays suitable to be driven by the Arduino and with contacts able to handle the current required.

I am sorry to sound so negative, but we are used to using very safe voltages when using the Arduino which means that we can develop a very Cavalier attitude to safety if we are not careful.

Hello,

First of all thank you for your prompt reply !
No problem for your "negative" advice, I fully understand it.

I have good experience of high voltage electricity : I have done the full electric installation of my house by myself, and pass the national exams , and my current work for already 5 years is light designer in a lighting manufacturer. So I know how to design and make electrical appliance.

I understand your worries about "software" danger. I will not connect to high voltage without test and trial on low voltage.

Regarding relays, I know the basics, how to connect, etc. But I only used them to light on and off bulbs.
I used them for testing lifetime of bulbs after multiple on/off cycles. i used arduino board to control one relay.

I think I will use a similar mounting, but with multiple relays.
Is there any specific brand for safe relay ? Or relay with multiple position ? like a 4 in 1 relay ?
I'm not sure to be very clear...

Thanks and best regards,

DImitri

Is there any specific brand for safe relay ? Or relay with multiple position ? like a 4 in 1 relay ?

A safe brand ?
Sorry, I can be of no help regarding relay brands. Obviously I would be suspicious of any random relay bought from Ebay, but but you should be safe if you buy from a recognised electronic component supplier such as RS Components, Element14 etc or the equivalent in your country. 4 gang relay boards are freely available on Ebay but I don't know what is available from reputable suppliers

relay board ebay

this is probably what you should use. a 4 gang optically isolated relay board. this one is generic, but lots of people have had good luck with them, including me.

if you really want to-do this "right" you might consider using contactors.

however doing so takes the cost from ~6$ to probably ~50-100$, so the choice is up to you. personally in a permanent install i would never use relays, but that depends on how much the typical load (amps) is. how many amps does the motor require to operate?

hope this helps!

Our multispeed cooker hood fan is controlled by a slider switch. If you are a mechanical engineer with electrical knowledge, then a row of four micro switches, suitably rated, would do the job. What was the original motor controller, why not use that? I guess you would like to venture into the uP world, but I think it would be better to start somewhere else, instead of here. The juice does not justify the squeeze, imnsho. Also, you have a button requiring maybe five pushes to turn off the fan, and you won't hear the low speed so that'll be left on more than you want.
Best wishes.

You may replace the Arduino by a 4017 decade counter IC, or something similar.

Button on the input to cycle through the five states (off and the four on states); relays to one output each. Makes sure only one relay will be on at a time.

You may have to add a small cap to the button for hardware debounce.

super7800:

this is probably what you should use. a 4 gang optically isolated relay board. this one is generic, but lots of people have had good luck with them, including me.

if you really want to-do this "right" you might consider using contactors.

the correct method is to know the application.
what is the current load of the motor for each stage ?
the relay has 3 ratings. an inductive load rating, a resistive load and a HP load.
Since you are using a motor,, the HP rating is the only one you need to look at.
as a rule of thumb, the Chinesse have a multiplication factor that is un-known.
for example, a common SSR (solid State Relay) has a 17 amp device inside. that is 17 amp max. but it is connected to a rather large heat sink, then labeled for 20 amps, 30 amps or 40 amps. depending on supplier and the label printer. So, the hidden multiplication factor is 1.2 to 2.5, unwritten, unknown and way over estimated.
that said, if the relay has a rating of 10, then you would be wise to design for your max load of 5.
as for the types of relay, I assume the motor is AC, in that case, the blue relay module might work well.
I would use an SSR as my next choice.
the contactor would only come into play if your motor is rated in the 1/4 HP or above range.
as a further note, the motor will have a centrifugal load so the starting amps will be in the lower ranges and pretty much any of the choices will work, as long as you are inside of the data sheet specs.

phase -II
if your stove top has temperature sensors and a persistent light indicating a burner is still warm after being turned off, you can sniff that circuit and control the light in the range hood and turn that on when any burner is still hot.

phase-III
find the data sheet for the SSR that controls the heating element, sniff that circuit. then tie in the Arduino to be able to control that SSR. you can then set your range heating to the heat setting based on the manufacturers controls, but interrupt it for a timed heating. My stove takes 6 minutes to boil 2 quarts of water.
I boil water, add rice, then turn the stove off for 4 minutes (glass heat top keeps boiling for 3) and at 4 minutes, turn the burner back on to the lowest setting for 4 additional minutes. then let the rice sit on the hot burner for an additional 8 minutes. Perfect white rice (Basmati)
This is screaming for an Arduino ESP-8266 so it can tell me that the rice is done and ready for some Aloo Mutter.

You can probably buy switches that do what you want, think old style radio buttons.

Your plan though sounds good. Each button press toggles the fan up a speed range and a long press turns things off. You might want to think about what happens if the fan is at "high" and the button is given a brief press. Does the fan stay at high, turn off or go to low?

The most important thing is that the cooker hood is silent. There is nothing worse than a cooker hood that sounds like a jet taking off. So if the hood is silent how will you know what speed the fan is running at. Perhaps you should consider a button that changes colour.

Using opto isolated relays is the safe way to go, make sure that they are rated for the voltage and current that you will be using and are a reputable make.

UKHeliBob:
For instance, is it safe to connect 2 or more of the speed control wires to 220V ? I know that this is not what you are anticipating but you must consider possible failure modes.

You “chain” the relays so that following relays commons connect from the NC of the preceding one. Simple. :grinning: