Small dc motor controller options

[hzuiel]

Hello, my application is a small aquarium circulation powerhead that has a sealed 12vdc motor in it that operates between 0.6w-3.9w, which i calculate is 49.9ma current to 325ma.

It is common in the aquarium hobby to cycle the power to these powerheads in order to create wavelike currents. I'm trying to research a way to power these using a controller of some kind that accepts 0~10v input for control. There are many aquarium monitoring systems that come witn 0~10v or pwm outputs for controlling various devices, but most manufacturers of the pumps do not design their systems to function with these inputs, and their wave making controllers are also ridiculously overpriced for probably a 3 dollar circuit board from china.

I have looked at some meanwell drivers that have 0~10v input but the smallest one i can find is the lpf-16d-12, 115vac input, output: 12v 1.2amp 16watt which is too much current, and not fine enough control. Roughly 1v = 10%, 2v=20% etc. 10% of the 1.2amp is 120ma, so at 3v it would exceed the pump's operating range, which if i understand the way the meanwell driver works, it only changes output at those intervals, so i'd have a 2 setting pump.

I would prefer the devices involved be mostly sealed in a plastic shell for obvious reasons, but an exposed circuit board isn't entirely out of the question if it's the best option. If it's necessary to diy a circuit board of some kind, I can solder.

In summary I need a DC motor controller for a 12v motor, with an output between 50ma and 325ma, and a 0-10v input for control

 

[hzuiel]

I also need to specify it can't be a stepped motor controller, it needs to be linear. I may also try a slightly larger motor which would be 0.6watt - 9.2watt, which is 50ma - 766ma range. Still probably too low to use that meanwell LED driver.

 

[Fish4Fun]

What is the switching time-frame? Are you turning it on and off more than 1 time per second? If not, why not simply use a relay and the existing power supply? Even @ 2 times a second for intermittent periods a good quality relay will do the job. Most DC brushed motors work best // longest if run continuously; the "starting current" is typically orders of magnitude more than the "running current", so continuously starting and stopping them can dramatically decrease their life-span. If you do need continuous short pulses (< 1 sec) you should consider a solenoid valve or interrupter on the output and leave the pump running continuously.

A 555 timer circuit could be used to control a relay for either your pump or a solenoid, and @ less than 1A draw you could even use a mosfet to drive directly either your pump or a solenoid valve. Ebay has plenty of 555 LED flashers for <<$5, adding a relay/mosfet and a plastic enclosure would be fairly trivial.

Fish

 

[hzuiel]

What is the switching time-frame? Are you turning it on and off more than 1 time per second? If not, why not simply use a relay and the existing power supply? Even @ 2 times a second for intermittent periods a good quality relay will do the job. Most DC brushed motors work best // longest if run continuously; the "starting current" is typically orders of magnitude more than the "running current", so continuously starting and stopping them can dramatically decrease their life-span. If you do need continuous short pulses (< 1 sec) you should consider a solenoid valve or interrupter on the output and leave the pump running continuously.

A 555 timer circuit could be used to control a relay for either your pump or a solenoid, and @ less than 1A draw you could even use a mosfet to drive directly either your pump or a solenoid valve. Ebay has plenty of 555 LED flashers for <<$5, adding a relay/mosfet and a plastic enclosure would be fairly trivial.

Fish

I don't just want to make them cycle on and off, they specifically need to be controlled in a linear fashion, and the controller needs a 0-10v input for controlling it so the aquarium controller system can directly control the pump. If i wanted to just power the pump on and off the aquarium controller can do that via the power outlets, but that's not what i'm trying to accomplish.

 

[Fish4Fun]

So, let me see if I have this straight:

You want a device that accepts a 0-10V control signal and outputs a regulated current range between 50mA and 766mA to drive an aquarium pump to produce a special effect; you prefer it be in a sealed, waterproof enclosure, but you think the existing products designed to do what you want are over-priced?

I think I have a pretty good grasp on the problem. Sadly, the solution is "You will likely be best off purchasing the unit designed to do what you want." Sorry, but unless you have some pretty good skills in electronic design/construction and want to pursue this as an intellectual pursuit, attempting to piece this device together with off-the-shelf boards from China is going to be difficult at best. The circuit itself does not need to be overly complicated (You could prolly use an LM337 as a current regulator and use an LM393 comparator with an op-amp or two and get pretty close to what you are describing); however, that does not imply there is a cheap off-the-shelf solution.

Good luck

Fish

 

[hzuiel]

It's not only about price, most of the wavemakers are self contained with no way to interface with the aquarium controller. Let me see if I can explain what the difference is. A regular wavemaker has pre-programmed modes that it maintains until you change them. If the pumps are controlled by the aquarium controller i can have it do different cycles at different times of the day, like stronger during daylight, lighter in the morning and evening and much lighter at night. To do this otherwise i'd need to be present at the aquarium every time of the day i wanted to change the wavemaker setting, assuming it even has a pre-programmed mode that does what i want. I can also set up a feeding mode more complicated than what most of the wavemakers have built in. LIke i can turn both pumps down to lowest setting, or turn one off and one down to half, however i need to adjust. If one mode doesn't work so well i can adjust it in the aquarium controller's programming. Cant change a pre-programmed feeding mode. Also in the case of a power outtage the circulation pumps will be on a battery backup, and the aquarium controller can be set up to turn them down to their lowest setting automatically when power is lost, to extend battery life. (without current flow in a saltwater tank, corals can all melt and die within a few hours of power outtage). This is just a few of the things that the aquarium controller can do that a simple(but extremely expensive) wavemaker can't do.

Examples of how expensive:
The pumps i plan to use are only about $40 each, but the wavemaker the company put out to run the pumps is 240 dollars. For that 240 all you get is some pre-programmed wave modes. It can't be connected to the aquarium controller in any way.

There are some 12v pumps that people found a way to cut and splice a control cable and connect it to the aquarium controller. One of the spliced cables is $20. Each of those particular pumps is for some reason $212.50. $445 total.

Another company has pumps that are on wireless controllers. They are $285 each and you need a wireless expansion module for the aquarium controller that is $125. $695 total and you're still stuck with the pre-programmed modes, but the aquarium controller can switch between them and scale the modes back by percentage.

This board is $6.95 http://store.qkits.com/moreinfo.cfm?Product_ID=553 is there no way this could be adapted to be controlled by 0-10v instead of pwm, and the output current be lowered with different resistors? I can figure a way to put a plastic shell around anything like this if necessary, or just locate it somewhere away from water contact.

 

[Fish4Fun]

OK, first I assume you have little experience with electronics, and I do not mean to be unkind, only making sure we are on the same page.

Next, the circuit you linked is a simple PWM speed control, using a 555 timer IC and a POT to control the duty cycle. It is absolutely possible to design a 555 based circuit to do what you want, it might even be possible to modify that PCB to achieve your goal; however, this would require some time/effort/knowledge that is probably not currently available to you and/or in your skill set. With this in mind you are in the position of relying on trial and error in an effort to make something work for a different purpose than it was designed.

http://www.ebay.com/itm/LED-DIMMER-PWM-10-A-12VDC-24-VDC-POT-0-10V-control-/270943921845#vi-content

Is a very likely candidate. I know you are going to protest that this supply is designed for up to 10A and you want to control in the mA range; however, I ASS-U-ME this is a straight-forward 0-10V to PWM Voltage converter which is exactly what you need. The good news is that this ebay seller ( http://digitallighting.com/ ) is based in Miami and is quite likely to have someone who speaks English answering the phone. I cannot promise this will work, nor can I promise that the person who answers the phone will be able to reliably predict suitability of this circuit for your purposes; however, for $44 delivered, it seems like it is a relatively cheap risk.

I know in CNC and other industrial applications 0-10V is commonly used for speed control. There are dozens of off-the-shelf controllers for this purpose; however, most of them are designed for far more robust applications than yours and are considerably more expensive than the above.

If you feel there is a larger market for such a device OR simply want complete control, AND you want to invest time learning about electronics, you might consider investing in an Arduino UNO prototype board. The UNO contains an AVR microcontroller which has 1000 fold more capabilities than this task, but it has the advantage of being designed for beginners and novices. It also has a relatively easy learning curve with a HUGE support network. With a very few external components you could easily achieve your task for less money than $44; however, time investment could quickly trivialize the cost. I would estimate an average beginner, with help would likely invest 100+ hours learning/researching/testing/debugging this type of solution. With any electronic/code project development time can escape geometrically and even the seemingly simplest things can spiral into countless hours, so take the 100+ hours with a grain of salt.

As a side note, I have been using saltwater pumps for over 25 years, though in a different venue. Maintaining saltwater systems is a continuous task and always expensive, lol. In my application it is for profit, not hobby, so justifying costs is more straight-forward, but no less challenging.

To recap (because I have been rambling) I am fairly certain you can make the ebay item linked work as is. If you want to invest some time/effort the Arduino UNO is a good starting place where there is a great deal of support available.

Fish

 

[hzuiel]

My experience with basic electronics is very limited, but I am very technically inclinded. I work with computers for a living. I was a traveling telecom contractor for 3 years, which might as well be called a mobile problem solver and multifuction puppet for corporate entities. They expected me to carry tools for, and have knowledge of systems ranging from proprietary phone, wired, and wireless systems, to industry standard analog and digital phone, dozens of types of wan broadband technologies, ethernet over fiber, copper and wireless, audio/video, intrustion alarm, cctv and surveillance systems. I am very good at systematic troubleshooting and I can solder. I am considering picking up one of those electronics learning lab kits and a book on learning electronics. Like I said, i am not opposed to DIY, but due to time constraints, an off the shelf solution would be preferrable.

What exactly do you do with saltwater system? Saltwater aquarium keeping is also a continuous and expensive endeavor. Some people in the hobby seem to have just adopted a mentality of "well it's expensive, so rather than try to save myself money, i'll just throw money at it." Not everyone is like that, DIY and modding is big in the community, but I just recently had a minor arguement with someone trying to make the case that a mediocre middle of the road 180gallon aquarium should run 15-20,000 dollars to set up, and shrugging at that kind of money like it's nothing. I think some people actually like to brag about how much they've spent vs what they've accomplished. There are many people successful at the hobby who haven't ever bought a new piece of equipment, everything they get is used, modified, or built DIY style. I notice you mention there being a larger market. I don't know that i would be designing something for resale, but it's possible if others like my design they may not feel confident setting it up themselves and might want to get one from me to try out. These would likely be very limited and not really for profit.

I may not fully understand but is any microcontroller on the board necessary just for the purpose of controlling the motor? All the logic should be coming from the aquarium controller(an expensive and complex piece of technology in and of itself). $44 dollars, even if i need 2 of them, is much cheaper than other alternatives though. Really the only satisfactory system to me right now is the two pumps and the spliced cable that adds up to $445 dollars which i mentioned earlier. Two of those controllers, two power supplies, and two pumps could likely be had for less than $170. I'm going to email their english speaking support to see if they have anything to say about my specific application.

 

[Fish4Fun]

Learning electronics => Good!

Saltwater System => I have owned a saltwater fishing tackle store with live bait for the past 28 years.

Is a microcontroller required? Absolutely NOT, but it is likely the cheapest/easiest approach in small quantities (<1000 copies). Even if someone were willing to design an application specific controller for you and give you the PCB artwork, you would still need to have the board made (~$100), and then source the parts and populate the PCB. An Arduino UNO is available delivered for ~$15 and with an additional $10 worth of parts you could be off to the races with a platform that is designed specifically for DIYers, but there is that whole "Time" thing....

The $44 controller referenced ***SHOULD*** work, but I can't promise it will.

Fish

 

[hzuiel]

I'm emailing their support now for that controller you referenced. I'll look into the arduino uno as well. Off the bat without help i wouldn't know which $10 worth of parts to buy to suit my purposes, either i'd have to acquire all the knowledge for it or someone would have to help me with a circuit diagram.

 

[pebe]

I also need to specify it can't be a stepped motor controller, it needs to be linear. I may also try a slightly larger motor which would be 0.6watt - 9.2watt, which is 50ma - 766ma range. Still probably too low to use that meanwell LED driver.

Are you sure the controller must be linear? It is much easier to design a circuit for PWM control.
Have you a datasheet or spec of the motor?

 

[Fish4Fun]

pebe,

Welcome to the forum!

By "linear" he means the motor is a 12Vdc brushed motor. And yes, he needs a PWM controller that takes an analog input from 0-10V. There isn't anything particularly difficult to design/build, but he needs/wants an "off-the-shelf", "ready to use" controller on a budget. By all means if you are aware of one share a link!

Fish

 

[hzuiel]

Unless I am not understanding the difference correctly, linear should provide much better control over the motor and much smoother operation when changing current back and forth.

I know digital pwm would probably be easier, but unfortunately the only available control method in the situation is analog 0-10v.

The motor is in a sealed packaged product, I could buy one and dismantle it to get more information, but currently all I have is that it's 12v, operating range 0.6watt to 9.2watt, and it pushes 240-680gallons/hour(which is totally irrelevant to this.)

 

[hzuiel]

The makers of that LED dimming module you linked said that it should work. The variable voltage was concerning me, because unlike an led that will only carry whatever forward voltage it will carry, you can over-volt a motor, but they explained that the board outputs whatever voltage it receives as input, so if I used a power supply that's a 12v constant power supply, it will output 12v. Similarly if i used a 12v, 750ma ac adapter, it would eliminate the possibility of it pushing too much current.

 

[pebe]

Looking at your #6 post, have you already got an aquarium controller that gives a 0-10V output, or are you starting from scratch? If you have the controller, what outputs does it give for fish feeding etc?

 

[hzuiel]

I haven't purchased it yet(starting from scratch), but the one I am planning to purchase is the neptune systems apex, which has 4, 0-10v outputs. It can be expanded with additional modules to add 4 more outputs each. Based on a lot of people's opinions, neptune systems makes the best quality controller, with the best support, for the entry level, which is why I was planning around it. As far as fish feeder control i'm not positive.

 

[pebe]

I had a look at the Neptune site. The bit about Apex was very vague about what it can do (typical sales blurb) - in fact, no detail at all.

I was hoping to get a feel for how it could do the things you wanted in the first paragraph of your posting #6. If I knew the details, it's quite likely a PIC micro could do what you want, and I could help you with that.

 

[hzuiel]

There is a product manual on their website with more details. I said EXACTLY the same thing when i looked at their website. Too much sales jargon, not enough info. But it has no pwm outputs, 1 serial connection with only software to support specific lighting fixtures, and (4) analog 0-10v dimming outputs.

 

[pebe]

I had a look at the Apex manual, but it really needs hands-on experience to know what it was talking about, so I tried various Youtube uploads instead. They were all just sales patter describing in a nebulous way what the unit would do. I discovered that you can feed your fish and watch them feeding with a webcam over the Internet. Wonderful! – does anyone actually do that? But I found a dearth of detail about how it is done, so I am no better off in knowing if a PIC could replace any of the functions.

For your information, a 14pin PIC has 12 pins that can be configured as inputs or outputs. They could easily be programmed to give 4 separate PWM outputs for 4 analogue inputs, leaving 4spare logical input/output pins for other purposes. The outputs can drive power FETs to give high currents if needed. So if you can decide just what you want to do, a PIC can probably be programmed to do it.