James, unfortunately it isn't digital so you are not going to be able to just type in a number and have it exact. The only time adjustment is by the nobs and a small adjustment as you note can have a large effect and the only way to figure out if you got the timing "precise" would be to sit there with a stop watch and check your adjustment.
There are digital repeat cycle timers out there but the pricing for those generally starts well over $100.
Or if you are good with electronics, you can make your own using pic axe chips that you can program on your computer, I've done that before.
Thanks much, TC! Your help is always greatly appreciated!!
I set the off cycle to minimum, which is a minute. The ON cycle I've had to set for a longer period of time than I actually need it, which results in the last two to four minutes of my flood cycle running over the top of the standpipes, which is fine, for my purposes - it just results in more aeration. When I try to reduce the flood time to the exact time needed it generally doesn't run long enough to completely flood some of my beds.
James Pahn said:
Maybe I am the only one person who don't know how to use this timer. I am having trouble to set the Cycle On at precise the time I want. For example, one munite and 30 seconds, 2 minutes and 15 seconds, etc. If I just turn the knob jus a little bit over 60 seconds, the Cycle On may last 2-3 minutes. If I switch the knob slightly counter clockwise, then the Cycle On may only keep working for a minute.
And to add to George's point, having the bed run flooded for a time while the water runs down the top of the stand pipe is actually a good thing since it allows a bit of extra time for the bacteria in the top flood level of gravel to get to work on the water. If you only just touch water to that point and then let it drain away immediately, that bacteria doesn't get to do much work for you. I always prefer to let the bed run at full flood with water going down the stand pipe for a time. Take note that the amount of time a bed needs water flow will change over time, for instance if something slows the pump a little bit like bio-slime build up, some pipe clogging, or a leaf partial blocking the intake, then it will take longer for the beds to flood, and as the roots build up in the grow beds, it will reduce the amount of water needed to flood the bed and therefore reduce the amount of time it takes to flood the bed. So, generally point in getting the timing down to the second when it comes to flooding the grow beds.
I would suggest " Intermatic " for a timer control unit. Intermatic produces a great many different timers and they are all solidly built. I think they are also made in the USA. I have seen a number of their times with the " push - pull " pins for setting the activation times for turning on and off. I believe they use a minimum of five minuets for the shortest cycle. I have several timers that use that configuration for my Hydroponics equipment. I would suggest checking some of the larger Hydroponics Stores. You could also use one of the numerous Digital Sprinkler Timers for activating in-line solenoid valves in the system.
I've never seen a mechanical intermatic that has pins or switches at 5 minute intervals. If you know of one, please post a link to it and where to get it. Smallest interval I've ever seen for the mechanical timers is 15 minutes.
Well I take that back, there was some one modifying some cheap intermatic timers that had been 1/2 hour intervals into a timer that would Take about 40 some minutes to go round and each interval was less than a minute. But those timers all quit working after only a matter of weeks.
As to the sprinkler timers and solenoid valves. Solenoid valves require a certain amount of differential pressure to operate unless you modify them, you also need to filter the water before it goes to those valves and clean that filter all the time so I don't really recommend solenoid valves for the average aquaponics system. And the timers for those valves can usually only do 4 cycles per valve per day. That is 20 cycles too few per valve in my book since I would normally send water to each bed once per hour. Now if you only have three beds and you get a six station timer I suppose you could gang together two stations to give you 8 cycles per valve but that is still not cycling enough water to the grow beds for most systems especially when you figure that the solenoid valves even drilled out and modified are going to restrict the water flow quite a bit. So if you go that rout I recommend you have some separate additional filtration that can run all the time for the fish.
As for inexpensive outdoor mechanical timers, I like the GE ones
they seem to work quite well, have the 15 minute interval, are for outdoor use, and I've only had one of them fail on me in the past several years unlike most of the other inexpensive mechanical timers that seem to stop working after several months.
Sylvia - Is this what you're looking for?
Let me know.