Hello!
My sister have a little business based on semi permanent hair dye (in fantasy colors -green, pink, etc.-) and it's really starting to take off. There is a technical disadvantage by making it by hand, and that is the difficulty to achieve a consistent color in different batches of the product. Sometimes the intensity is notably lighter or stronger, other times the tone isn't the same.
I've proposed to investigate the possibility to make an automated arduino mixer, using just cyan, magenta and yellow ink (CMY color space) to achieve the 12 colours in the pellete. My first idea was to use washing machine electric valves, as they are easy to get and cheap, and to mix the different proportions of each ink by controlling the flow time. But there I found an inconvenient at using this method, as the inks are going to be made by hand, and the concentration is probably going to vary in a way that screw the final result. I could just tell her to use some lab equipment to prepare the ink in a more consistent manner, but the idea is to make it simple to make. So I had the idea to use a color sensor and continually read the color of the mix and add drops of the missing color to correct the mix gradually until the desired color is achieved.
What do you think about this approach?
Can you think about a better way to make it?
The inks come in powder, and need to be diluted in alcohol before apply it into the product, and about 1 to 2 grams are all that's needed to make a few liters of the dye, that's why it's not easy to mix it in a very consistent way in the low volume we produce.
Sorry for my bad English (Spanish is my mother language)
Interesting idea but to have any chance of being accurate (assuming the sensor is up to the job) the measuring environment needs to be properly controlled so no ambient light can effect the reading.
eliasg13:
Can you think about a better way to make it?
How about jewellery scales to accurately measure your powders?
That would make it cuite easier to make acurate ink preparations.
About the controled enviroment i was thinking about a servo with a stick. It would go down and sip in the preparation to get a samnple and get it to the sensor in a black box, so the only ligth source is the one frome the sensor itself.
I know that making consistent inks would simplify the proyect a lot, but i'm also interested in the challenge to make it in a closed loop system.
I belive it would also serve the purpose of cuality control, and maybe to add the "Copy Color from sample" function.
Electronics aren't that great at fine color recognition, and measuring out liquid ingredients electronically is also tricky. This is a long term project, is what I'm saying. Multiple non-trivial tasks.
I think the short term solution is better process control - precisely measuring the components added to the mixes and doing it the same way every time. Solid ingredients should be used by weight, not volume, because of airbubbles and differences in the density of lumps of the material vs powder. Larger batches are typically easier to control, as the precision of any specific measurement doesn't need to be as high.