Circuit setups for pulse motors

[hoptoad]

@Ren
" I can vary current consumption. I am still testing. It will run on 25ma up to 300ma, higher with less resistance. I currently run it in between 60 and 100ma for a reasonable speed. This is without a load (well the wheel is 1.5 kilos +) BUT charging on the backend. Funnily enough it doesnt consume much more @ 24v.
Mechanical loading only causes the current consumption to drop as per all ssg circuits. I only ever run it with a charging bank connected as to ensure the safety of the circuit, i.e no blowing the transistors. Testing showed that current can drop a little when a charging bank is connected."........................................

Ren, assuming a Voltage supply of 24 Volts, then at 100 milliAmps the total power consumption of the circuit is 24 x 0.1 = 2.4 watts (forget duty cycle and assume straight DC for the purpose of simplicity.)

Now assume the worst, and your motor's electricity to motion efficiency is only 50%, then a maximum of 1.2 watts would be wasted as heat energy. Thats not a real lot of wasted power, and your coil has 3/4 of a kilogram of copper mass to effectively dissipate it. It should heat only very slowly.

Now assume optimistically, that your motor's electricity to motion efficiency is 80%, then a maximum of 0.48 watts would be wasted as heat energy. Your coil with its great mass would probably not notice a thing, because copper is a great conductor and radiator of heat to the environment.

Again assuming a Voltage supply of 24 Volts, then at 25 milliAmps the total power consumption of the circuit is 24 x 0.025 = 0.6 watts
Assuming the worst again and your motor's electricity to motion efficiency is only 50%, then a maximum of 0.3 watts would be wasted as heat energy.

Assume optimistically that your motor's electricity to motion efficiency is 80%, then a maximum of 0.12 watts would be wasted as heat energy.

It's very easy to see why things remain cool. We're not talking very high power wastage figures here. Throw in a few downward adjustments to your meter readings due to actual duty cycle, and the power consumption (and heat loss) is less than you think - Thats where your desire to get an oscilliscope (scope) is in need of fulfilling. Good luck with saving for your measuring  hardware! It aint cheeeep cheeeep! KneeDeep 

[Ren]

I see. So something that draws more should show some signs of heating. My window motor draws up to 1 amp and the coil can get slightly warmish. Its alot thicker and shorter though, being about 1mm thick. Transistor doesnt heat at all though. Im tossing up between a traditional scope and a usb one.  They are both in the 300 bracket.

I meant to ask too. I have been looking for an expanded analogue meter that reads between say, 10 and 15 volts, primarily for battery voltage readings. You mentioned somewhere that you had switched to these in an attempt to clarify your readings. Can you tell me where you got yours?

[hoptoad]

I meant to ask too. I have been looking for an expanded analogue meter that reads between say, 10 and 15 volts, primarily for battery voltage readings. You mentioned somewhere that you had switched to these in an attempt to clarify your readings. Can you tell me where you got yours?

@Ren,
I bought mine via a catalogue from JayCar Electronics. I'd been to Sydney to visit a friend for a few days and popped in to JayCars for a browse and grabbed one of their catalogues. I ended up buying two analogue meters with a maximum range up to 20 volts and 10 Amps. They are Russian built and weren't cheap at the time. I paid $65.00 each for them, which was a lot of money in 1991 ! But they were worth the investment. Especially since I couldn't afford a scope which averaged around $1000 +  at the time.

" Mechanical loading only causes the current consumption to drop as per all ssg circuits."...................

This makes sense (I keep thinking traditional Adams motors, but you're using a sensor pickup coil). When the rotor slows, the voltage and current available to the sensor coil decreases, which in turn decreases the amount of signal to the switching transistor, which in turn decreases current availability to the drive coil. In effect, the SSG arangement is a self protecting one, in which it is nearly impossible to burn out your main drive coil due to excessive loading.

" Testing showed that current can drop a little when a charging bank is connected."........................

This is a very good indication that your motor is running harmoniously and that the regenerative circuit is not causing the Virtual Duty Cycle to exceed 50%. - Well done.! 

@Casman - You may be failing at achieving O/U, but I'll wager that you are creating some highly efficient motors, and having a lot of fun while you're learning from your constructions. 

Cheers All from The Toad Who Hops 

[Ren]

Thanks Toadie.

I'm well known there (Jaycar) but I asked about it and they dont have anything like it. I read about a way to modify a normal meter with resistors etc to read your desired range somewhat. Otherwise I am at a loss. I have a good analogue meter up to 250ma but it reads in 10v and 50v increments, making it pretty much useless for voltage tests on 12v batts.

I am starting to see the effects of this charging on the battery too. It only starts to happen when the battery is charged and discharged repeatably daily.

I am building a bicycle wheel rotor at the mo... 16 poles NSNS config to experiment with pick up coils etc. Already twisted and wound a trifilar awg 18 approx 150 feet for a decent sized coil! I want to create a commutator which will accomodate various functions, one being backpopping the primary. I still have a bit of work to go, but I'll post some pics soon.

Im glad that the sg circuit is very sturdy. I dont think I have blown one when its been installed properly.

[hoptoad]

Thanks Toadie.

I'm well known there (Jaycar) but I asked about it and they dont have anything like it. I read about a way to modify a normal meter with resistors etc to read your desired range somewhat. Otherwise I am at a loss. I have a good analogue meter up to 250ma but it reads in 10v and 50v increments, making it pretty much useless for voltage tests on 12v batts.

I am starting to see the effects of this charging on the battery too. It only starts to happen when the battery is charged and discharged repeatably daily.

I am building a bicycle wheel rotor at the mo... 16 poles NSNS config to experiment with pick up coils etc. Already twisted and wound a trifilar awg 18 approx 150 feet for a decent sized coil! I want to create a commutator which will accomodate various functions, one being backpopping the primary. I still have a bit of work to go, but I'll post some pics soon.

Im glad that the sg circuit is very sturdy. I dont think I have blown one when its been installed properly.

@Ren
Good luck with your next round of experiments. The dual pole magnet configuration and tri-filar drive coil will allow for a very wide range experiment parameters, especially if you include the option of a separate trigger coil as well. Then you can play around with all three filaments in your drive coil. I have no doubt you will be surprised by the results of certain configurations!

Pulsed motor systems are full of fun surprises, e.g. Doubling the supply voltage does not automatically double the current draw, but always increases running speed. Think about Inductive Reactance and how it increases with frequency!

Your existing 17 ohm's DC resistance coil filaments can easily exhibit a total Impedance at 1000 RPM of 300 ohms or more. With the rotor spinning  1000 RPM, with 8 magnets, the pulse frequency will be 8000 PPMin which is 133.33 PPSec. Double the number of magnets (i.e 16) with the same rotor RPM will result in a pulse frequency of 266.66 PPSec.

You'll notice a much greater output from any pickup coils that you add to the perimeter of your motor, than the output from the a mono pole arrangement. Also, the power signal generated in any separate pickup coil will be true AC. In a mono pole arrangement it is actually a varying DC signal which mimics to some degree, true AC, but it is DC just the same.

I did a quick google for analogue meters (Australia only): heres the results page below:
http://www.google.com.au/search?hl=en&q=analogue+multimeter&btnG=Google+Search&meta=cr%3DcountryAU

Cheers and KneeDeep