Variable frequency drive pump controller?

[bprewit]

Ok just an idea and probably a bad one but was thinking about this and figured would see if anyone else has ever considered this. The reason I even though about something like this was the fact that there are alot of options to create currents in a tank. From SQWD's to powerheads attatched to wavemakers, to the oceansmotions, and lots of others. Powerheads are unsightly to alot of people and some other drawbacks like impellers breaking over time from constant starting and stopping when hooked to a wavemaker. I was trying to figure out how to make a surge type device in my tank, without spending a ton of cash and lots of the surge devices I have seen were pretty large and most were to mounted inside the tank. So I put my simple little mind to work and came up with this but no idea if it will actually work like I hope. If I were to have two seperate pumps in a closed loop configuration each pumping water to oposite ends of the tank. Starting and stopping the pumps almost like a powerhead wavemaker, but with enough large diameter outlets and enough volume to create lots of flow going from one end of the tank to the other to move lots of water but not in concentrated streams like a powerhead output. Large pumps like mag drives wouldnt handle being turned on and off constantly I dont think plus it would be pretty violent flow going from full on to full off. So my idea was to use a Basic Stamp 2 to drive a IGT or Mosfet pulse width modulation control. So I would have a variable speed control for the pumps. They would never stop completly but instead they would speed up and slow down at a rate determined by the program in the basic stamp. I think using the stamp as a controller you could run a series of programs creating higher and lower flow instead of one constant flow rate. Parts for such a thing would be fairly cheap as less than $100 and no I dont really need this for my tank and there are lots of other options to do something like this I know, was just bored and curious if something like this would work. I think I will try and build a simple circuit in the next few days to play around with as I have plenty of parts laying around and have the stamp controller. Any input on why this would or wouldnt work?

[Tim Marvin]

Tunze 6060 and 6080's work fine. I run a SQWD with them and it breaks up the current well.

[NaCl_H2O]

I'm not a EE, but have lots of EE coworkers and I ran some similar thoughts past them awhile back. As you said, I think the controller could be put together rather easily and not to expensive. The downsides that I thought about were:
- Pump motors need a minimum current or duty cycle to keep spinning, and I assumed only the more expensive pumps would offer much flow "variability".
- As a pump collects calcium deposits, it's minimum torque requirements will change
- I received some warning that the lower quality pump motors may not hold up to his type of control very well

I bought OM Squirts and have been very happy with them ... minimal maintenance and my pumps all run full speed 24x7.

[bprewit]

There are lots of products to create random currents I know and they are all proven and work just like they are supposed too. I was just bored and trying to think of something to do so came up with this. I actually am a pump mechanic/electrician for oilfield equipment. I install and set up lots of pumps on soft starts as well as variable speed drives, all which use PWM control so thats kinda where I got this stupid idea from. I figure its something to play around with and keep my mind occupied. I am concerned about the pumps overheating like you stated as they are not really designed for such a application, large motors for use on VSD's usually are rated as "inverter duty" and have insulated bearings and higher class insulation on the windings to deal with the excess heat created and random currents in rotor shaft that cause the bearing to rock back and forth causing premature failure. Maybe this will work, maybe it wont, but if it does it will be pretty cool!

[MikeDeL]

Keep working on it. If you have the spare parts, time, and ambition. This is how new and improved products are created. Maybe one day your "stupid" idea will make you rich. :D

[NaCl_H2O]

Maybe this will work, maybe it wont, but if it does it will be pretty cool!

Agreed! Post your results either way - we learn a little from our success, but mostly from our failures ;)

[bprewit]

Well I ordered a few parts today to try this little project out. I changed the design a bit after finding a easier way to do things, still using the basic stamp as a microcontroller but using triacs instead of mosfets or igt's. Triacs arent the greatest for controlling inductive loads as they limit the current by pretty much cutting out part of the sine wave, but for the low wattage of the pumps they should work great. I ordered a triac control chip that was designed to be used to control inductive loads with initial soft start then speed control so it should work pretty good. I will post if it does actually work! If nothing else comes from this it should atleast provide soft ramp of pumps like Seio's for basic wavemaker type setup and extend the life of the impellers without damaging the windings while working a bit better than the existing soft start wavemakers that you can buy.

[GaryP]

Since you are in the biz, are you aware of any less expensive industrial sources for pumps such as Iwakis. My understanding is that they were originally designed as chemical transfer pumps and found a new home in the aquarium industry. As with many things, a lot of technology gets moved to new markets with a shiny new "hobbyist" pricetag.

[bprewit]

Unfortunatly there arent alot of them in use as oilfield equipment. Most of the industrial labeled pumps like iwaki are used more for lab equipment, photo developing, and such. The chemical pumps that I see all the time are small pumps identical to the dosing pumps that are so **** expensive. I could probably come up with some new unused dosing pumps for really cheap if not free but have no use for one. There are a few good things that I get from work that are usable on the aquarium though. I just got a couple of 400W MH pendants that work perfectly, mogul base, only thing wrong is the glass shield is broken which is pretty cheap to replace. I will check around though and see if I can come up with anything like the iwaki pumps for better price than the aquarium labeled market.

[captexas]

I would be worried about the wear and tear on the pumps. You will need to look around and find heavier duty pumps that are designed to handle a range of electrical current. I know there are some out there as I've seen that info before, just can't remember off hand which manufacturer it was. If I find it, I'll post here. It is an interesting idea if you can get it to work. We run into VFDs occasionallyat work with some of the malls we have equipment in. They use them to control their A/C equipment. Unfortunately, VFD's put a ton of electrical noise back on the main lines and cause problems with our anti-shoplifting systems. Only fix is to install some expensive filters on the malls VFD units.

[GaryP]

I am very familiar with oilfield chemical pumps. I used to be a chemical man. The only time they would use a pump like we use would be on a chemical delivery truck of for transferring from a bulk tank into a day tank. Most olifield chemical pumps have to be adjustable in order to meter dosing. Its hard to go that with a centrifugal pump. They mainly use piston or diaphramn pumps. As I think you were mentioning they sometimes use peristaltic pumps.

They are mainly used for low volume, low pressure applications. The good thing about them is that you don't have to worry about contamination. All you have to do is change out the tygon tubing.

[bprewit]

Well found easiest way to do this yet! $50 on ebay won me two small VFD's. Once they finally arrive I will figure a controler of sorts using the basic stamp and see if this will work.