Electronic Circuits and Projects Forum

With the 74C14 it doesn't matter if the inputs are HIGH or LOW. Just don't leave them floating. With some 4000 series the inputs need to be HIGH to take the least current.

I take your point Colin, but simulation shows that the voltage drop is less with R3 = 3k3 than with R3 = 1k.

That's faulty analysis.

The impedance of the 24v line is much lower than the 12v line.

I don't have a power supply yet, anything that works, is durable and reasonably efficient is perfect in my book.

I just ordered the pumps & they won't arrive for a couple weeks or so. These pumps come with a controller set up for 220, I have 110. Also, the controller that comes with this pump does not do what I need. I don't know what the pumps will do with 12V compared to 24V. If you think it would be worthwhile, I could run a 220 line and see. There's no way I want 220 anywhere the aquarium. BTW, there are two other choices for DC pumps that perform in a similar fashion that are set up for 110, but they cost in the range of $500 each!!! I need six pumps, I can't afford that.

I'm up for hooking this thing up any way that works. I hope I have this right-I was going to get a 24V, minimum 6A wall wart/transformer.

If each pump is rated 30W, that is likely be the continuous power and implies a steady current of ~1.3A. However, the start-up current will be considerably higher, perhaps 3A or more? So for 6 pumps you're looking at a supply which can handle say 18A briefly and 6 x 1.3 = ~8A continuously without being stressed. I doubt you'll find that in wall-wart form, but it should be readily obtainable.

I agree 100% with all of this ^ ^ ^ ^.

I don't have a power supply yet, anything that works, is durable and reasonably efficient is perfect in my book.

If you don't have a power supply picked out yet, there are some good, cheep, and easy to work with units on ebay. I just searched with the term "24v power supply", and organized it by "best match" to find good ones for this project.

Make sure what ever you get is greater than 250 watts, or greater than 10 amps. I personally would aim for 20A or 480W myself. Units with fans built in are the best IMO. My only complaint with any of these units is that they are all way to open and exposed. This is needed for ventilation, but this also makes you more endanger of electrocution and fire should you accidentally dump your reef tanks *salt water* on it. Make sure your careful where you place your power supply and have all your stuff hooked up to safe outlets with the proper protections (GFCI outlets on their own 5~15 amp breaker). You also could and should spend the extra cash and get a waterproofed power supply for outdoor use. Your looking at spending more than $70 just for a power supply this way though. But your life and home is prolly worth more, am I right?

Also, If you have to (If you use a smaller power supply) you can work around the high surge currents alec_t is talking about with a few fatty NTC resistors and maybe a tank capacitor. It's not ideal, but this can make the power supply not switch it's self off as soon as the pumps start. We can also come up with something else like an active soft start circuit if need be. But we will cross with that bridge when we come to it.

OK, my simple take, and correct me if I am off target is these are 30 Watt 24 Volt aquarium pumps. So we get about 1.25 amps per pump. Pumps of this type are more a circulating pump than a pump that does considerable work. If a tank sits several feet above the floor and the pumps on the floor, other than circulation the pumps do not do any real work, they simply move the salt water. I am guessing you are simulating a reef. So with 4 pumps running the current would be about maybe 5 amps. Allow a margine maybe a 7 amp power supply.

I realize a 7 amp power supply does not take into consideration inrush current when the pumps start, however, I don't see it as a concern. Even if all 4 pumps were to start simultaneously, since they are circulatory pumps I don't see inrush current as an issue because of the type pumps they are. I don't see it as an issue that could not be solved using a capacitor at the power supply output beyond any internal capacitors to the power supply. Keeping in mind these pumps are not pushing a column of water uphill that is not being pushed downhill at start.

As to the 120 / 240 volts. Without seeing what exactly comes in the box it becomes hard to call. If sans the actual pump power the controller mentioned draws little current then a simple small transformer might be a viable solution. Low power control transformers are inexpensive.

Just about everything goes back to what's in the box. Colin & Alec have both posted really good timing circuits. A link to the actual this is what's ordered would be real nice about now.

Just My Take
Ron