DC12V 12A car window motor - what spec for a 220V PSU?

[jim hardy]

I tried using a 24V 50mA lamp.

That's only 2.5 ma at the primary where the dimmer is.
Transformer steps primary voltage DOWN from 230-ish to 12, and current UP from 2.5 ma to 50 ma.

You'll need a 12 volt two to four amp lamp..
Wattage comparable to what works on primary side.
Can you borrow one from an automobile? Brake, turn signal or headlamp ? Dome light won't do.

Don't despair , this is Edison's '99% perspiration' complement to his '1% inspiration' .

Mother Nature likes to see us sweat.

old jim

 

[Asymptotic]

I can get the speed down to 29 rpm @ 5.3V 4.7A (using the slow charge switch on the charger).
35 rpm @ 6V 5.1A (using fast charge switch)

(It looks like that 5A fuse is too light)

Difficult to be certain, but 5A may be 'just right', or perhaps even too high. Problem is, the motor was designed for low duty cycle, intermittent operation from a DC battery source, and has been re-purposed to serve in a high duty cycle design fed from a rectified power source. Ultimately, both fuse elements and motor windings fail due to excessive heating, and for sustained overload protection the trick is to select a fuse that will clear before motor windings are damaged. Off-the-shelf, general purpose, continuous duty motors are typically rated for a 40°C temperature rise. You'll probably be OK by closely monitoring motor heating until you are comfortable it isn't about to become a flambé.

I haven't looked up the clearing curve for a BS 1362, 5A fuse, but came across this interesting article comparing 3 amp and 13 amp fuses, and learned a 3A fuse will hold on indefinitely at 4.5 amps. My guess is for a 5A fuse it'll be on the order of 7.5 amps.

I vaguely recall IEC standards having something similar, but NEMA DC motor ratings include a "power code". Power code A is battery powered (PWM output is between A and C, although close to A than C), code C (nearly all the motors I worked with were code C) is DC derived from a full wave bridge, and code D is rectified DC from a half wave bridge. One way to overheat a DC motor is to feed it voltage with an 'uglier' waveform that what it was designed for. For example, I've seen FHP (fractional horsepower) motors cook when their drives lost an SCR, and effectively morphed from code C to code D.

Given this, my guess is part of your motor heating is a consequence of the supply waveform. If you have a largish (in the 100 to 330 uF range) electrolytic capacitor handy, temporarily clip it across the battery charger output, and see what happens. The motor ought to run cooler, and provide smoother low speed operation.

It looks like your project is coming along nicely. Kudos.

 

[Tom.G]

Hey guys, after sleeping on it I realized the added resistive load must at least equal, preferably exceed, the inductive load; and will probably be more effective when connected to the dimmer. What say @jim hardy , how much must the resistive load exceed the inductive load to keep the TRIAC on? Taking account of both phase shift (power factor) and leakage inductance of a very low cost transformer

If put on the xformer secondary there is still the leakage inductance etc. on the primary side. If put across the motor (after the rectifier), there is the additional problem of not being connected around zero crossing. Those may be enough to upset the dimmer.

Yea, the above is weasel-worded. That's because I've never tried the resistive load on the secondary and would be interested in the result. On the primary we know it works. If you care to teach all of us, try it on the secondary and enlighten us. (Some oscilloscope traces would be nice if you have access.) If you just want to get the project done, keep the resistance on the primary.

 

[jim hardy]

how much must the resistive load exceed the inductive load to keep the TRIAC on? Taking account of both phase shift (power factor) and leakage inductance of a very low cost transformer

If put on the xformer secondary there is still the leakage inductance etc. on the primary side. If put across the motor (after the rectifier), there is the additional problem of not being connected around zero crossing. Those may be enough to upset the dimmer.

All above is true.
Resistive load need only pass holding current of triac at end of trigger pulse
and since we don't know what is value of that holding current or duration of trigger it'll have to be found by experiment what size lamp does the job.

He has an advantage in not needing full AC voltage, that's easier on the transformer (remember volt-seconds and saturation) .

Trial and error is the approach for this one. See if a 40 watt 12 V lamp on secondary behave noticeably different from a 40watt 240 volt lamp on primary ?
To avoid rectifier drop he could connect it here

old jim

 

[marcophys]

Pauses in development are useful.
They are usually caused by external forces, but in fact they are anyway required.

I must clear up something else tomorrow, and then I'll get back on this.
I'll implement the fuse as suggested, and then look again at resistive loads.
I have the typical 240V lamps and 12V auto lamps.

Thanks for the considered thoughts.

 

[marcophys]

I haven't looked up the clearing curve for a BS 1362, 5A fuse, but came across this interesting article comparing 3 amp and 13 amp fuses, and learned a 3A fuse will hold on indefinitely at 4.5 amps. My guess is for a 5A fuse it'll be on the order of 7.5 amps.

Okay, the 5A is implemented

Given this, my guess is part of your motor heating is a consequence of the supply waveform. If you have a largish (in the 100 to 330 uF range) electrolytic capacitor handy, temporarily clip it across the battery charger output, and see what happens. The motor ought to run cooler, and provide smoother low speed operation.

Found a 330 µF 25v capacitor on the PC PSU board.
It was difficult to desolder.
The solder cooled instantly before the solder pump could work
... but got it out.

330 µF 25v capacitor across DC output

This had a similar noise reduction effect to the lamp across the dimmed mains supply.
IE. buzzing reduction

I then added the 40 watt lamp to the dimmed mains suppy.
The noise reduced even further.

It was already only a slight hum with the lamp (as per video), but clearly, both primary and secondary sides can be cleaned up.

However - having just wired it in the capacitor 'popped'!
So it failed.

This renders some of the questions (below) irrelevant at this time.

Q. Capacitor safety?

When removing the capacitor... should I simply short the two connectors across metal?
It sparks of course.
... but is that the correct procedure?

Q. Is the capacitor the superior option to Jim's concept of the lamp?

IE. should I solder it internally, and will it be fine for normal battery charging use?

Q. If the capacitor option works on the secondary side, should it be considered for the primary?

I have a large range of capacitors of varying voltages etc.

 

[marcophys]

Further thoughts... and note that the capacitor failed in the edit above.

Transformer Sound Clarification
With the ear on the transformer chassis:

When powered by standard mains supply
The transformer hums.
In addition: there is also an inconsistent minor ticking

When powered by dimmed mains supply
The transformer hums.
In addition: there is also a 'fast' consistent ticking - 'loudest volume'

When the lamp is applied, the ticking 'slows' - noise volume reduces

There appeared to be a similar effect with the capacitor, but I had no time to reconfirm before it failed.

While awaiting thoughts on the capacitor... I will test Jim's idea of a 40 watt lamp across the DC output.

Result

If the primary has no lamp in parallel... there is a reduction in the transformer ticking.
However... when a 40 watt lamp is across the primary
... placing another 40 watt lamp across the secondary makes no difference.

I think that an oscilloscope would be really useful for these tests.

Hopefully though, the results might enlighten.

The fact is that the lamp and capacitor had a noise/ticking reduction effect and
the lamp and lamp didn't.

 

[marcophys]

Notes on the popped capacitor

LTEC LZG 105 deg PET 8628D
http://www.compostar.com/Ltec/LZG.pdf

It had seen use in a PC PSU.
The top was flat when tried.

I'm wondering if I could have damaged it during soldering.

I'll look for an alternative.

 

[marcophys]

SAMXON 680 µF 200v LP (M) 85 deg (has polarity)

This was a major success vis a vis visible effect.

Test Method - Lamp & Capacitor

With 40 watt lamp across the primary
The motor was slowed to the absolute minimum.
If stopped... the motor could just restart.

The capacitor was placed across the DC output... the vibrating hum noise of the motor subsided to just a hum.
IE. the motor sounded better.

Without the 40 watt lamp and without the capacitor
The motor would not start.

The capacitor was placed across the DC output... the motor started.

Conclusion
Having a capacitor across the DC motor supply allows the motor to run better!

The SAMXON capacitor (22mm D x 41mm L) is physically much larger than the LTEC capacitor (8mm D x 16mm L).
It is 200v compared to 25v.
Also it has polarity.

The LTEC capacitor got hot.
The SAMXON capacitor remained cool.

Test Method - Lamp & Lamp

The same as above.
The primary lamp was removed... the motor would not start.
The secondary lamp was applied... the motor would not start.

To confirm... the capacitor was applied... the motor started.

Therefore it appears that the 40 watt lamp across the secondary, has no effect.
Whereas the capacitor across the secondary has a strong positive effect.

Questions

Was the choice of lamp incorrect... or is it simply the case that the capacitor provides the correct solution?

Is there any reason to test different capacitors... or has the objective been achieved?

 

[jim hardy]

I'd say your capacitor works.

The LTEC capacitor got hot.

Feel the new one for heating

When the triac "fires" it injects a large and brief pulse of current into the capacitor to replace the charge that the motor consumed since last charging interval in the immediately previous sine wave.

. Short but intense bursts of current have high heating value, look up "Crest Factor RMS" .
Here's first hit i got and it's a pretty good explanation.
http://www.programmablepower.com/support/FAQs/DF_Crest_Factor.pdf

I suspect the "Ripple Current Rating" of your small capacitor was exceeded and that's why it got hot.

Keep an eye on the bigger one's temperature for a while. If it stays cool you're fine.

This is how we learn !

old jim

 

[marcophys]

Final test of this session
Confirm the need for the dimmed mains supply 'solution'.

With the capacitor wired in parallel with the DC output & the 40 watt lamp in parallel with the dimmed mains supply ...
... the motor was slowed to absolute minimum, yet could be stopped and started.

By removing the lamp... the motor would not start.
The test was repeated.

With the lamp... the motor would start.
Without the lamp... the motor would not start.

Conclusion
A solution is required for both the AC supply to the transformer, AND the DC supply to the motor.

Notes
I note that Jim concurs that the capacitor is the correct solution for the transformer DC output.
The capacitor seems to remain very cool - no apparent change in temperature.

I have justed tested the minimum rpm... 8 rpm.
It is the lowest yet recorded!

When you think we started with the lowest rpm at 54 rpm.
... we now have fingertip control down to 8 rpm

What Next?
Here's the 'motor speed control panel':

For test purposes, a two way adaptor allowed a two pin socket to be placed in parallel with the dimmed mains supply.

This was an excellent solution.
The lamp holder, cable, and plug are ancient (and filthy)... but they worked perfectly, and provided a constant for all the tests that followed.
To test with, or without the lamp... the lamp plug could be easily inserted or withdrawn.

It seems that, while we can love the lamp solution because it works (and has character)... can it be replaced with something more robust?

A smaller lamp could be found, and mounted in the transformer to provide a protected environment.
... but I'm thinking that it does not provide closure.

Clearly, running at 130 volts AC it is unlikely to fail.
However, there must be a replacement that is more suitable.

I think that it is worth trying because, we no longer need to have the option for insertion and withdrawal.
It's the final leg of the development process.

However... if the lamp concept proves to be the best... perhaps an oven lamp is the ideal option:
http://www.ebay.co.uk/itm/2-x-25w-240v-Clear-300-Degree-High-Temperature-Oven-Lamp-SES-E14-Light-Bulb/401347623192

14mm screw thread and the lamp is short and narrow.
It appears to be one of the smallest 240v bulbs available.

 

[Asymptotic]

Whoops. I ought to have mentioned the same waveform ugliness the capacitor helps to filter from DC output necessitates a higher voltage rated capacitor than what one might at first expect. @jim hardy pointed out the culprit is crest factor, which can be thought of as a measure of the ugliness of an AC waveform.

Q. Capacitor safety?
When removing the capacitor... should I simply short the two connectors across metal?
It sparks of course.
... but is that the correct procedure?

Shorting poses two problems - 1. very rapid discharge rate doesn't do a capacitor any favors in terms of longevity, and 2. particularly true of capacitors used in larger equipment, enough energy is stored to melt terminals and screwdriver tip, and splash molten metal about. For cap discharging, a useful piece of kit is an insulated 50 ohm, 50W resistor with leads and alligator clips soldered to it.

Q. Is the capacitor the superior option to Jim's concept of the lamp?
IE. should I solder it internally, and will it be fine for normal battery charging use?

I wouldn't say either is superior to the other. Using a lamp (resistor) and capacitor in tandem should yield better results than either one alone, since each of them are attacking different aspects of the problem of low speed control quality.

 

[jim hardy]

I actually like the combination though i don't quite understand why it works so well .

old jim

 

[marcophys]

Yes... that halogen lamp is even smaller, and would sit rigid between solid cores :)

Alternative to the lamp concept

CGS HSA50 1.8k Ω resistor
Typically used as demister heating elements in camera housings, beneath the glass face of the housing.

I do believe that somewhere I have a spare.
Annoyingly, I had to raid this one from a perfectly good housing
... but they are readily available if another is needed.

I calculate that @ 130V it is consuming 9.4 watts 0.072 amps
I believe that the 40 watt lamp at 130V is consuming 11.7 watts 0.09 amps

Therefore very similar.

I wired it to another two pin plug; allowing a perfect test comparison with the lamp.

Result
It does the same job.
Both start and turn the motor at slowest speed.

The advantage is that it can be easily and securely mounted to the chassis, which in turn will dissipate the generated heat.
It would appear that this is the correct solution.
----------------------------

Wow!
I think that's it.
What a journey - started in complete confidence that we would arrive

.. I had to, just now, load the first post.
All we had was a window winder motor as the core element, and a concept.
Everything was then fabricated from what I could find.
Nothing was purchased (saving weeks of time).

18 days, from start to finish.
... and the turntable is entirely functional, and safe.
It lacks nothing of importance... the talk of a tachometer was just talk... it's not needed.
It is a serious 'working product'.

Wouldn't it be nice if the banks would support engineers?
The chances of them funding a stock purchase of base engine components is slim to nonexistent.​

Either way... It was a great team effort.
... and it is all documented.
Hopefully it will help the next generation.

Sincere thanks to all contributors... it's a shared victory, and it was a pleasure.

 

[Asymptotic]

I actually like the combination though i don't quite understand why it works so well .

View attachment 207884

old jim

I don't know why, either.

1970's era Reliance Electric MaxPak engineered DC drives had a resistor (12K/25W springs to mind, but it could have been something else) wired across the S-6 bridge upstream from a definite purpose (DC) contactor. Don't recall seeing them in later iterations (MaxPak Plus), or used by other drive manufacturers, and don't know for sure why one was used in the older design. My guess is it acted as a minimum load to prevent armature feedback voltage from reading high due to normal SCR leakage current after the motor armature was switched out of circuit by the DP contactor.

The 12K resistor didn't provide enough load to scope SCR operation without a motor connected (although a series pair of 240V/500W tubular heaters worked a treat) so that wasn't its purpose.

 

[Asymptotic]

Yes... that halogen lamp is even smaller, and would sit rigid between solid cores :)

CGS HSA50 1.8k Ω resistor
Typically used as demister heating elements in camera housings, beneath the glass face of the housing.

This 50W wire wound resistor ought to work just fine ...

... and for the project overall, Huzzah!

 

[jim hardy]

Feel that resistor for temperature. It'll want to be mounted to some metal , as you pictured it, to dissipate the heat .
But you knew that.

Thanks for sharing your fun project with us .

 

[marcophys]

Wow!
I think that's it.

... or is it?

Tidying The Loose Ends

The 2 speed motor
We never discovered how the motor reduced speed when it's polarity changed.
Jim put it down to mechanical or electrical wizardry

That's a perfect holding position for the moment.
The spare motor/drive will be opened in the near future
... It looks like the screws will fail, so it will become a major job.
If I take it apart, I must then put it together again... so I'll leave that for the moment.

The battery charger
We never analysed it.

I always assumed that everybody else understood it... and everything seemed straightforward.
... but came the time to begin modifications, and everything was not as it seemed (to me).

I had been metering only DC voltage
... but in fact, everything appears to be AC voltage.

I also found that 'apparently' with the addition of a switch (slot already provided)
... the charger can also provide an output of circa 6 volts DC
OR
circa 12V AC
OR
circa 24v AC

Q. Did everybody know that already?

According to the meter... anything outputted, metered as DC, is doubled when metered as AC.
The suggested wiring contacts for the lamp (by Jim) shows 0 volts DC & 14V AC.
(so it is not just a case of doubling or halving the metered voltage)

I'm just wondering why we didn't attempt to rectify the AC voltage output?
I'll make a video of all the metered results, but what are everybody's thoughts on this?
It certainly seems that with the addition of a single switch, the charger can provide 6V

Here's the wiring diagram against the charger image:
Note the marking of the 6V & 12V outputs metered as DC.

 

[jim hardy]

I had been metering only DC voltage
... but in fact, everything appears to be AC voltage.
...
Q. Did everybody know that already?

Not I. Looks to me like it'd be DC. Unfiltered DC which has a LOT of AC content, but DC. Those two heatsinks look like a rectifier.

The suggested wiring contacts for the lamp (by Jim) shows 0 volts DC & 14V AC.

I expected that, it's why i picked that spot. It's upstream of the rectifier.
Try this...

With no load and no dimmer,
read charger output voltage with DMM set to DC. You should read around 14 volts DC.
Switch DMM to AC volts. It should read less maybe 1/3 as many volts

Now connect your capacitor across charger output + to -.
Read voltage again with DMM set to DC. You ought to read nearly 18 volts.
Switch DMM to AC volts. You should read one volt or less.

If all that happens then i understand the charger. Mother Nature loves to fool me, though.

Going back to this image for a moment
(even though likely it's upside down- dimmer is probably in the hot wire ? )

Your charger and motor are connected in place of the lamp.
When Triac fires the dimmer becomes an effective short circuit, ie voltage across it collapses.

Inductance of the motor postpones current rise so triac may misfire , as we described earlier.
I've noticed that myself using treadmill motors with a bridge and a lamp dimmer. They won't start at low settings.
Your capacitor across the motor accepts a big gulp of current at instant triac fires so i understand that part.
The resistor across transformer primary also accepts current, though less of it, so that's why Tom.G's lamp worked. I understand that.

There's probably an optimal combination of R and C. But don't argue with your success.

What i don't understand is your statement

everything appears to be AC voltage.

It contains both an AC voltage component and a DC voltage component.
Most DMM's will read them separately depending on what they're set to- AC or DC.
But SOME high quality True RMS meters will report just that, the true sum of both DC and AC components, when set to AC. That'll fool you if you have one of those and aren't aware

Place a small capacitor, maybe 0.1 or .0.01 uf , in series with your meter's red lead and see whether that affects its reporting of AC volts.

That's why old analog meters like Simpson 260 have their "Output Jack" , to block the DC component out of a waveform that has one. It places a 0.047 (i think) capacitor in series.

I'm probably all wet on that one but it should be checked. It's fooled me before.
Ya Juat Gotta know your test equipment..

old jim

 

[marcophys]

Thanks Jim.
I was merely reading the meter @ AC & DC settings.
... but let's see what happens with your tests.

With no load and no dimmer,
read charger output voltage with DMM set to DC. You should read around 14 volts DC.
Switch DMM to AC volts. It should read less maybe 1/3 as many volts

All readings below taken on

• Mains supply
• fast charge setting
• no load

DC output = 13.5 V
AC output = 29.1 V

Now connect your capacitor across charger output + to -.
Read voltage again with DMM set to DC. You ought to read nearly 18 volts.
Switch DMM to AC volts. You should read one volt or less.

• capacitor connected across output

DC output = 20.6 V
AC output = 44.8 V
--------------------------------

Okay Jim... I'll stop there, because the recorded AC voltages are unrelated to your theoretical projections.
Perhaps the results may indicate a different understanding.

I thought that the heat sink was a capacitor
Check my drawing for details.
(-ve to -ve & +ve to +ve show no connection when metered for resistance)

 

[jim hardy]

I'll stop there, because the recorded AC voltages are unrelated to your theoretical projections.

That's too much AC . I don't know what's happening. Myself i'd suspect the meter is doing something that i do not expect of meters.

I'll try on my charger.

 

[marcophys]

That's too much AC . I don't know what's happening. Myself i'd suspect the meter is doing something that i do not expect of meters.

I've metered it again, on both fast and normal charge (without capacitor across output).
in both cases AC is showing slightly more than double the DC.

Re the capacitor.
I've found a couple of 50V 0.1 µF capacitors.
I also came across an RBV 602 bridge rectifier
https://www.digchip.com/datasheets/parts/datasheet/139/RBV602-pdf.php
http://pdf1.alldatasheet.com/datasheet-pdf/view/38177/SANKEN/RBV-602.html

 

[marcophys]

I fitted the RBV 602 to the output - the two centre pins.

The two outer pins (marked + - ) delivered similar readings... AC just more than double the DC.
I presume that this confirms that something is amiss with my meter.

Anyway, having got the rectifier... I'll see how it works with the motor.

 

[jim hardy]

Your tenacity is to be admired !

 

[marcophys]

Your tenacity is to be admired !

Thanks Jim.
But to be fair, it was alarm & confusion that was the driver.
Seeing AC everywhere on my meter.
I needed this confirming, not only for this project, but for future metering.

It seems that you are right - my AC meter shows just over double the DC value, even after passing through the bridge rectifier.
Anyway...

I wired the RBV to the charger output, and then wired the capacitor across the rectified output.
My thinking was that, either way, the RBV would likely clean up the voltage further.
Placing the capacitor last was simply the easiest for testing.
Perhaps the capacitor is best placed in the charger, where you suggested the lamp position.

RBV 602 Results

If 4V DC is seen at the output
... 3V DC is seen after the capacitor
... 2V DC is seen at the motor (10m 1.5 sq mm cable)​

The RBV gets hot
The capacitor remains cool

The RBV therefore requires mounting on aluminium.

Motor

• Quieter
• It sounds better
• It operates down to 7 rpm (1.7Kg load)

This looks like it is the limit, due to a tight spot, either in the gearing or drive shaft alignment.

Ideal Component Positioning

1.8k Resistor
This can be positioned on the voltage control board, and wired across the socket outlet.

680 µF 200V Capacitor
Currently located after the RBV rectifier.

Options

• Pre charger rectifier (Jims lamp photo)
• Post-charger rectifier (IE. the traditional output)
• Post RBV rectifier

I'm going to try it at pre-charger rectifier.
It is a convenient location point, and it should tidy the supply to the rectifier.

 

[marcophys]

Ha!
No... it was a failure.
(Damn... I spent an age creating the wiring art)

Result
The moment that I switched the motor on... I knew.

The first thing was that it wouldn't start - it needed more power.
... then the sound.

I had another capacitor, so I quickly placed it after the RBV.
This confirmed that the capacitor should be the last component.
... meaning that it, and the RBV can be mounted on the motor switch control panel.

Q. Is there any reason to keep the capacitor mounted in the charger case?
It's nicely mounted, so it can stay... if we think that it must be helping somewhat.

 

[jim hardy]

Whoah ! You wired your capacitor IN SERIES with the transformer return lead. That'll blow it up.
EDIT
oops i missed one wire
i still think you have it on AC side so that's why it'll blow..

It has to go in PARALLEL and AFTER the rectifier.

 

[marcophys]

Well... I wired it as per your photo:

"Trial and error is the approach for this one. See if a 40 watt 12 V lamp on secondary behave noticeably different from a 40watt 240 volt lamp on primary ?
To avoid rectifier drop he could connect it here"

It shows 12V AC with dimmer feed... so it is in parallel.

 

[marcophys]

I have changed the wiring of the internal capacitor.
It is now wired across the output -ve and the +ve entry to the fuse, similar to Jim's recent suggestion above.

Result
This worked.

I then wired in the 2nd capacitor after the RBV.
The motor was slowed to 6.5 rpm.

I then disconnected the 2nd capacitor, and the motor would not run.
Re-connected it... and the motor ran.

From this it would appear that the motor benefits from the 2nd capacitor.
Perhaps this just means that the 680 µF 200V Capacitor should be increased.

Note
These speeds are at the absolute minimum.
The motor actually 'cut-out' momentarily after stalling for a few seconds..

Perhaps there is a thermal overload within the motor casing.
There seems to have been no damage - it runs fine now.

I'm only running at 'stall speed' for test purposes.
... and it is proving a useful tactic.

The Problem (with an internal capacitor)
The DC voltage output is 20V DC.

I placed a 240V 40W lamp across the output... it was still 19.5V.
My first thought was that this would prevent the battery charger from being used as such.
However, I then thought about the dimmed voltage.

Without any additional switches or wiring within the charger
... I can now dim the voltage down to whatever is desired.
This should mean that I can use the charger for both 12V & 6V batteries.
... a definite 'side effect' win

The RBV could be mounted within the charger chassis, but I'm now of a mind to locate it on the 'motor switch control panel'.

On that I'll pause.
I need to sort out all my heat sinks, and see how best to do it.

Overall
... my failure to mount the capacitor correctly has added to our knowledge.
As usual, it has raised another question... as to 'what is the ideal capacitor value'?

But these are details.
I now need to physically wrap up the project - get everything securely and safely mounted.

I'll then take some photos, so that the system can be seen

 

[Tom.G]

Perhaps this just means that the 680 µF 200V Capacitor should be increased.

Depends on what you are after. The higher the capacitance the higher the average DC voltage under load (within reason). Adding the external RBV rectifier just subtracts about 1.5V delivered to the motor, hence the lower speed.

Knowing the @jim hardy expertise with graphics and detailed explanations, perhaps he can come up with some waveforms and average versus peak voltages. My quick mental calcs indicate to reduce the ripple voltage at the motor to 1V would need roughly 10 000uF with a 1A load on the charger output.

@jim hardy : Sorry to put you an the spot here, but the conversation seemed to need steering to a better understanding of the phenomena... and I'm otherwise occupied for a bit.

p.s. The different fwd/rev motor speeds may be that the brushes are rotated with respect to the field windings, often a design choice.

 

[marcophys]

The different fwd/rev motor speeds may be that the brushes are rotated with respect to the field windings, often a design choice.

Ah... so we are not completely in the dark

Wrapping up what we have achieved

Motor control panel
As you can see... I fitted the resistor onto it's heat dissipating aluminium bracket
... and then fitted the bracket to it's natural place, only...

The plug flex would tend to lay on the resistor, which is not great.
It means that it will need a flex guide, if I keep the resistor in this position.
(it's a typical prototyping error... you can never think of everything, until it's done, and then...)

Battery Charger - Motor PSU
This shows the mounting of the 1st capacitor, and wiring into the output

Motor Switch Panel
I hear what you say Tom, re the RBV.
Subjectively, the motor seemed to run better - I swapped it in and out a few times.
Anyway I kept it, and mounted it on an aluminium heat sink, with an alloy plate on top, to further improve heat dissipation.
Heat paste was also used.

The 2nd capacitor was kept because, again subjectively, the motor seemed to run marginally better.
The capacitors run cool... I could barely feel any warmth
... as a result, I've tie-wrapped it in place... it was simply convenient.

The 5A fuse is between the RBV +ve and the main switch.

I need to tidy the exposed connectors... but it's pretty much there.

Last main job is to bridge the switches.

Very pleased with it.

 

[jim hardy]

I'm a bit confused as to what we have now.

Is RBV a bridge rectifier
Where is it installed and connected ?

What is the "Second capacitor" ?
680 or 0.1 ?
Where is it connected ?
Where is the 0.1 connected ?

The Problem (with an internal capacitor)
The DC voltage output is 20V DC.

That must be with the 680 connected AFTER the bridge on its DC side ?
Will dimmer not drive it lower ?

Can you mark up that sketch & photo from post 88 ? It was great !

old jim

 

[jim hardy]

I really don't think some ripple will hurt the motor and it'll help it make torque at low speed. That's how electric drills work.

I need confidence that the schematic in my mind is the schematic we actually have .

How's it working ? I get conflicting thoughts

The Problem (with an internal capacitor)
The DC voltage output is 20V DC.

Without any additional switches or wiring within the charger
... I can now dim the voltage down to whatever is desired.

in same post

 

[marcophys]

I'm a bit confused as to what we have now.

Understood.

It's the universal difficulty in documenting change.
... the current status as compared to previous status (and maybe in the same post, a mention of the planned mods).
Of course, the writer knows what's happening, but as for everybody else...

Is RBV a bridge rectifier

RBV 602 bridge rectifier
https://www.digchip.com/datasheets/parts/datasheet/139/RBV602-pdf.php
http://pdf1.alldatasheet.com/datasheet-pdf/view/38177/SANKEN/RBV-602.html

Where is it installed and connected ?

Mounted on an aluminium heat sink, with an alloy plate on top, to further improve heat dissipation.
Heat paste was also used.

The two centre pins are AC - directly fed by the input connector at bottom.
Red left passes thru the fuse to the primary motor switch.

What is the "Second capacitor" ?

SAMXON 680 µF 200v LP (M) 85 deg (has polarity)

Where is the 0.1 connected ?

Place a small capacitor, maybe 0.1 or .0.01 uf , in series with your meter's red lead and see whether that affects its reporting of AC volts.

This related to my meter reading AC at a DC outlet.
I haven't done this test yet

Can you mark up that sketch & photo from post 88 ? It was great !

Yes I will.

The funny story (funny to me) is that I should already have drawn a digital diagram.
I sketched it out first, and was unsure how the heat sink/rectifier worked.
Then I thought oo... maybe I can just upload it as an image... I'll just pop it into Gimp.
... and that was it.
I spent ages trying different filters & mods.
A new drawing would have only taken ten minutes ​

I will draft the diagram... and then perhaps the community can explain why it does what it does.
At least... I now know it uses a bridge rectifier.
This should help.

 

[jim hardy]

Thanks man, you are a good explainer of things !