Speed Controller Problems.... please help

[CoggesRailway]

Hi All,

I am doing a couple of cheap and cheerful battery engines. The first is literally go/stop/reverse. This is suprisingly effective for watching the train go round, apart from ungraceful starts and stops... So i decided to try one of these: http://www.maplin.co.uk/panel-mounted-speed-regulator-module-30310
This does the trick but makes the motor whine horribly even when stopped. Any thoughts.? I think it may be doing a similar thing to what dcc does to analogue motors.
Also it only operates above 6 volts. Does this mean that I will get a very short run from a 7.2v 3000mah battery or doesn't it work like that? could I exepect the battery to stay above 6v for an hour with a single lgb motor and small train?

Ian

 

[whatlep]

Hi All,

I am doing a couple of cheap and cheerful battery engines. The first is literally go/stop/reverse. This is suprisingly effective for watching the train go round, apart from ungraceful starts and stops... So i decided to try one of these: http://www.maplin.co.uk/panel-mounted-speed-regulator-module-30310
This does the trick but makes the motor whine horribly even when stopped. Any thoughts.? I think it may be doing a similar thing to what dcc does to analogue motors.
Also it only operates above 6 volts. Does this mean that I will get a very short run from a 7.2v 3000mah battery or doesn't it work like that? could I exepect the battery to stay above 6v for an hour with a single lgb motor and small train?

Ian

Ian - the unit uses pulse width modulation (PWM) and that's the source of your problem which is potentially quite bad news for the motor. PWM means that the output voltage is sent as a series of pulses so the motor never gets a smooth current flow. Basically it is being switched on and off very rapidly and the motor is getting a full blast of the available voltage every time it's on. I would take it off to avoid potential damage to the motor.

I recommend you use a miniature potentiometer instead, plus a centre-off DPDT switch for direction and battery switch off. Others will be able to advise you on the best resistance value to use. Save the knob from your speed regulator for use on the potentiometer.

 

[coyote97]

its pulse width regulated.....that means that the voltage is not regulated with its definite high amplitude. Its more that the voltage has a constant amplitude and the effective voltage is created by cracking the constant DC-signal in parts.
The number and width of those steps gives an effective voltage that makes your motor going faster or slower.

advantage: it does NOT "steal" power like spool-regulator, witch turns all power not needed into warmth.

disadvantage: its noisy, because u do not use constant voltage. the "stepped" voltage brings your motor to make sounds. The frequency you hear is the frequency the modulator gives out.

7,2V 3000mAh is not that bad, it should move for more than an hour.
My Bachmann Connie has a 2300mAh lead accu and i can play (PLAY, not DRIVE) for 3 or 4 hours with it. I often go up a grade of 4% on about 15meters length with some cars on the hook, so, its quite a heavy duty, even though i dont move all the time.

The 3-motor-shay with the same battery runs for an hour or something like that.


if the controler will take 12V, i would change to 12V lead accu (cheap) or 11,1 V LiPo (expensive but somehow not to get down...)
low voltage always means more current to get a powerlevel. As the signal-width-controlers work on ONE voltage level, u will get more effectivity, the higher u can go with voltage level.


Greetings

Frank

 

[Rhinochugger]

I use one of the Cambrian speed controllers in this little beastie. Speed is controlled by turning the exhaust pipe

 

[Rhinochugger]

It is a Worsley Works etched kit of the IoM Viking, running on an IP Engineering 0-6-0 chassis (no longer available - but see LC Models by KGR).

I re-engineered the gearbox & motor a couple of winters ago, and the whole thing runs quote well now - 14 axles for about 4 hours as far as I know, never got to run it for longer.

 

[Del Tapparo]

Nothing wrong with PWM if used at higher frequencies. Older designs used low audible frequencies that make that horrible whining sound. Doesn't sound good, and actually can heat up the motor a bit. New designs, such as all of my products http://1stclass.mylargescale.com/DelTapparo/gscalegraphics_1_005.htm < Link To (G-Scale Graphics) use higher frequencies (20KHZ), that you can't hear and the motor likes.

 

[CoggesRailway]

Thanks chaps. yes i have disconnected it... bit of a waste of £15!

Could someone place a link of what I DO need that would be really helpful....

 

[whatlep]

Thanks chaps. yes i have disconnected it... bit of a waste of £15!

Could someone place a link of what I DO need that would be really helpful....

Ian - for a definitive answer we need to know what voltage you will use with the loco and how many milliamps the motor consumes. The reason is that as those two factors vary, so does the resistance best suited to the potentiometer (pot or variable resistor). I'm guessing that a 3 watt pot would be best suited to your needs and probably one in the attached link http://docs-europe.electrocomponents.com/webdocs/0aad/0900766b80aad9a5.pdf which is from RS online http://uk.rs-online.com/web/ .

 

[Del Tapparo]

The trouble with using a Potentiometer is all of that wasted power! It just cuts down on your run times. Using a efficient PWM controller, all of your mah go to the motor, not wasted in heating a potentiometer.

 

[CoggesRailway]

thanks peter. It is a single buhler motor so I guess no more than an amp. The most voltage will be 7.2v.....

 

[whatlep]

The trouble with using a Potentiometer is all of that wasted power! It just cuts down on your run times. Using a efficient PWM controller, all of your mah go to the motor, not wasted in heating a potentiometer.

Very true and the bad news is that the higher the wattage (volts times amps) the higher the cost of a potentiometer too!

Ian - I'd be surprised if your motor was taking an amp, even pulling a big load. I think you either need some experimental data before going too much further down the road with this or to bite the bullet and spend some dosh! As Del Tapparo rightly implies, a PWM speed controller designed for model railway use may end up being the best way to go. For example, a Brian Jones "Chimp" controller is £39.50 plus P&P if I read his price list correctly http://www.brianjones.free-online.co.uk/page5.html . A 6 amp pot is £35+ and you only have a bare bones system. If you can use a 3 amp pot (max current probably only 250 milliamps) the price is a lot lower (£13-ish), but you'd have to be sure about the motor's current draw and your battery voltage before buying.

 

[whatlep]

A small extra thought. If you really want to go cheap and cheerful, you could take an "N-way" rotary switch, where "N" = the number of batteries you intend to use (say 6 at 1.2 volts for 7.2 volts total) and tap one end of each battery to the "N" terminals effectively creating a stepped 1.2-7.2 volt feed to the motor. You'll need a centre-off DPDT too for on/off as well as forward/reverse. It will be jerky of course and you'll need to figure out how you'll charge the cells, but it would be cheap! If this doesn't make sense in words, I can draw it for you...

Here's an example switch: http://www.maplin.co.uk/rotary-switches-2417?ordercode=FF74R

 

[trammayo]

I use the IP Engineering controller - it will certainly cope with 3 to 12 volt. I have been running it for five years now with my portable layout - up three or four Big haulers sometimes - and certainly two or three for up to 7 or 8 hours continuous. Simple rotary control feeding a Darlington transistor with a diode.

 

[whatlep]

I use one of the Cambrian speed controllers in this little beastie. Speed is controlled by turning the exhaust pipe

I assume it's one of these - type 2? http://cambrianmodels.co.uk/speedc.html
Remarkable pricing! I presume that there aren't any nasty noises from the motor?

 

[trammayo]

H'mm - the Cambrian ones look like they are "horses for courses" where as Ivan's is a "one size fits all". Mine is the latter type and works extremely well if I may give credit to it. There are NO harmonics from this unit. The PW technology (I had a 5amp one for the garden) is very annoying and might be detrimental to motors. I am considering using 12 volt (battery) again and another IP type control for the garden having proved its worth over the last 5 years!

PS. A heat sink is a very useful adjunct to mount the transistor on. I used a (or my brother did!) a piece of scrap ali about thre square inches in surface area.

 

[CoggesRailway]

I''ve ordered IP ones....

 

[Madman]

I must enter into the discussion here. I was very hesitant to make the switch to battery power. That is until Del Tapparo answered many, many, of my concerns, PWM being one of them. I have several of his units. Both the R/C versions and non R/C versions. I run LGB almost exclusively. I have not had a single issue with PWM and the LGB motors. The only minor issue I have is with the very simple LGB steam sound unit that I pulled out of the 4035S box car, and installed it in the battery car. This particular sound unit is not crazy about PWM. So when power comes on at start up, the steam sound is already at top speed. On the other hand, I have an LGB sound unit from one of their powered tenders that works perfectly with Del's products. Power comes on to the motor. The train starts to move slowly out of the station, and the chuff sound follows the speed of the accelerating train. I am now almost a complete battery convert. Thanks in no small way to Del.

 

[CoggesRailway]

Thanks Madman - I did like the sound of Del's one's. I think if PWM doesn't hurt the motor and make an annoying noise it is preferable - apparently the low speed motor torque is much better. However i have decided to go the old fashioned way mainly because Del is on the wrong side of the pond and I want to carry on with my project on Saturday!

 

[GAP]

I have a small diesel (an old MDC Big Hustler) that I have used with batteries and an LM338K variable regulator to control speed. The O/P voltage of the regulator is variable from 1.2V-32V, with max current of 5 amps, and requires minimal componets, I fitted all mine on a 2.5"x1.5' piece of veroboard. I used this circuit to make some controllers for my old HO layout and they are still working well after 15 years, to obtain 0V at the minimun I just put 2 diodes in series with the O/P to drop the 1.2V. I used a DPDT centre off switch to control direction and the adjustable resistor shaft was disguised exhaust pipe.

 

[Del Tapparo]

I have a small diesel (an old MDC Big Hustler) that I have used with batteries and an LM338K variable regulator to control speed. The O/P voltage of the regulator is variable from 1.2V-32V, with max current of 5 amps, and requires minimal componets, I fitted all mine on a 2.5"x1.5' piece of veroboard. I used this circuit to make some controllers for my old HO layout and they are still working well after 15 years, to obtain 0V at the minimun I just put 2 diodes in series with the O/P to drop the 1.2V. I used a DPDT centre off switch to control direction and the adjustable resistor shaft was disguised exhaust pipe.

I did my first ever battery power job this way. But again .... It is a power/battery wasting solution. But if you get enough run time and don't overheat things. It works just fine!