Timer with short intervals

Ok, so I built an air pump-driven autodoser (only did 1 pressure bottle of the 2 is made so far), but I'm having trouble limiting the amount of air that makes it into the bottle in a minute on the digital timer. It seems that I'm getting 3x the amount of liquid that I want to dose at each interval. I'm still testing it with water and the sink, so I can try out different ideas before I install it and make the other half.

Does anyone know of a plug in timer that allows for intervals of 30 seconds or less?

How about ideas for restricting airflow to the bottle? I currently have a dial valve (like the petco gang valves) to restrict it, but can't go any lower without the system losing too much pressure to beat the head loss.

I'll make a DIY video out of the other bottle that I make, I'm just trying to figure out this last problem so I know this can be completed.

 

bump

 

I tried doing something similar to what you are. I eventually gave up because I couldn't get the dose tuned well enough to be comfortable with it. I never could find a timer programmable to the second either. Down to the minute with 20 daily settings was the best I personally could ever find. It's a GE Digital sold at HomeDepot for $10.

 

I found one with 8 settings and down to the minute; the real problem is the pressure buildup in the bottle over that long of a period. It makes it so that nearly regardless as to how low you set the valve from pump to bottle, it's not low enough to stop quickly (5 mLish) but high enough to make it up to the tank.

I just wonder how the one that tatted4ever had works, because that's pretty much the same concept.

 

I had one that went down to 1 minute intervals. It was a digital Intermatic one. I don't know if you will find one hat does 30 second intervals.

 

I'm not sure what you're dosing but maybe you can just dilute the solution 3x with RO/DI water so that you're getting only 1x the amount of "product" with each time unit dosed?

 

look for "recycling"" or "interval" timers at greenhouse supply shops. I know I have seen second:minute interval timers where you can set them for 1-999 seconds/minutes on then 1-999 seconds/minutes off. Each knob has a switch.

there are 1440 minutes in 24 hours, so you could have it on for 20 seconds then off for 720 minutes and dose 2x a day...

Here's one, $125: http://www.hydrofarm.com/pb_detail.php?itemid=8010
Here's another, $85: http://www.discount-hydro.com/productdisp.php?pid=73&navid=7

 

I saw some digital timers for hydroponic setups that had pretty low intervals but not sure they went as low as 30 seconds.

 

how about putting a micro ball valve on the fluid output? this would restrict flow instead of restricting the time it is on...