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[on:]

A neat little project idea I've had is a little module with a three buttons (small, regular, and extra large loads), that automatically dispenses the correct amount of liquid laundry soap into the washing machine.  (it's a front loader with a lid/flap on the top that you open and pour the liquid soap in as the water runs through it).

Any ideas on how to somewhat accurately measure the detergent out?

[Reply #1 on:]

A lot of Rube Goldberg-ish things come to mind

[Reply #2 on:]

In commercial laundry applications such systems are very common, using large containers of detergent, fabric softener, etc. Think small low volume, high pressure pump and either a timer, # of piston pulses, etc determine how much detergent gets dispensed. It's open-loop control but good enough given that the clothes washer can determine how much detergent it needs from analyzing the load in it and the program selected.

[Reply #3 on:]

If you do actually use some sort of low pressure pumping system a liquid flow meter, like this one, might be useful.  The linked meter sends a pulse after ~2.25 ml, and least for fluids like water.  For more viscous fluids like laundry soap you may need to characterize it.  In any case, while not extremely accurate or precise, it should be sufficient for the task at hand.  There might be others even better suited, I just don't know of any off-hand.

[Reply #4 on:]

If you do actually use some sort of low pressure pumping system a liquid flow meter, like this one, might be useful.  The linked meter sends a pulse after ~2.25 ml, and least for fluids like water.  For more viscous fluids like laundry soap you may need to characterize it.  In any case, while not extremely accurate or precise, it should be sufficient for the task at hand.  There might be others even better suited, I just don't know of any off-hand.

I use one of these to automatically measure the water into my coffe pot.  Doubt it would be accurate enough for just a quarter cup of high viscosity detergent.

[Reply #5 on:]

I use one of these to automatically measure the water into my coffe pot.  Doubt it would be accurate enough for just a quarter cup of high viscosity detergent.

Ok, but it might be worthwhile to see if there are similar flow meters intended for measurement of viscous fluids.  I'm sure the have been in exisitence for quite a while, the real question would be is if any available that are affordable for a hobbyist-type budget.  One possible lead would be looking for the parts used in automatic hand soap dispensors.   

[Reply #6 on:]

http://www.amazon.com/Brushless-Submersible-Water-Ideal-cooling/dp/B0051HI3OM/ref=pd_bxgy_sg_img_c

I got one of these to try...  An electric hand soap despensor would be good to check out alright!

[Reply #7 on:]

An electric hand soap despensor would be good to check out alright!

My guess is that those type of units rely on a diaphragm pump of some kind. They are usually a bit more expensive than the volute-pumps used for water and other low-viscosity liquids. Making them last a long time in contact with detergents, bleaches, and so on may be a challenge. Good luck!

[Reply #8 on:]

Another method would be to have your machine mechanically press the pump (with a cam or a solenoid) on a standard liquid soap dispenser, like this one:
http://www.foodservicewarehouse.com/thunder-group/plsd377/p366978.aspx
Could vary quantity by number of pumps, timing, etc.

[Reply #9 on:]

A peristaltic pump would be the proper method. They are also kinda crazy expensive, but making one from scratch should be pretty doable with a small, high torque motor (those $5 stepper motors or an RC servo).

[Reply #10 on:]

Look into finding a dosing pump. I use them to keep proper levels of calcium, alk in my aquarium automatically, they are quite accurate.

[Reply #11 on:]

Pre-measured containers with open/closed valves, and a float valve to stop pump when full.....

i don't think you would even need a micro controller for that....

[Reply #12 on:]

I saw your post and wanted to know if you have had any luck dispensing the soap. I have been in touch with the sullivan pump company (they make fuel pumps for the RC hobby industry. They recommended the S752 fuel pump, though they did caution some uncertainty with laundry detergents with bleach.

Please let me know. I plan to make the same circuit, but doubling it to also dispense fabric softener.

I know the pump works even with thick fluid (I tried with my costco laundry detergent. It takes about 20 seconds to get to the middle line at 12V

If you have a sketch, I could use it to save me a lot of trial and error programming.

Thanks
 

[Reply #13 on:]

I use one of these to automatically measure the water into my coffe pot.  Doubt it would be accurate enough for just a quarter cup of high viscosity detergent.

Don't know about the dishwashing soap, but.... do you have any info or site describing your coffeepot setup?

New over here on the Home Automation board...

Cheers,
John