Re: [EVDL] Cheap DC motor control anyone?

[ROBERT via EV]

I would go the variable speed drill direction.  Lee, from my experience SCRs 
have a tendency to false trigger on noise.  I was burn a few times.  I remember 
using a GE SCR for an alarm circuit.  I could not get it from false triggering. 
 I talked to the SCR designer at GE and he never could come up with an answer.  
I redesigned using transistors and NAND gate chip and everything was OK.   
Another possible choose is to look on the web for a motor speed controller kit. 
 I think Jameco makes a kit.  One time, I purchased a motor controller from a 
local surplus store.  I suggest looking for a controller that works  forget 
a one off design.



From: EV <ev-boun...@lists.evdl.org> on behalf of Jan Steinman via EV 
<ev@lists.evdl.org>
Sent: Friday, January 26, 2018 4:58 PM
To: ev@lists.evdl.org
Cc: Jan Steinman
Subject: Re: [EVDL] Cheap DC motor control anyone?

> From: Lee Hart <leeah...@earthlink.net>
>
> David Chapman via EV wrote:
>> Lee I really appreciate the lead
>> on the GE handbook, I downloaded it and indeed that circuit on pg 293
>> looks perfect for this project…

So, it sounds like one of the goals of the project is to put something together 
from components?

Because I thought Lee’s idea of finding a variable-speed electric drill at a 
thrift store or yard sale was really an excellent idea.

You can probably do so for less than the costs of buying components, especially 
if you’re going to pay “single piece” shipping on them.

And the drill speed control has the advantage of having been designed for motor 
speed control. Newer ones even use pulse-width-modulation, which you can tell 
if it makes a squealing or whistling sound at low speed. That sort of 
controller is going to give you the best low-speed control, with lots more 
torque.

 The more the work is left to nature, the greater the net yield but the 
longer the time required... Thus sometimes the most apparently productive and 
high-yielding sources of energy involve a lot of activity for little return, 
while long-term investments, especially in naturally grown forests, provide the 
greatest value for future generations. -- David Holmgren 
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LMGTFY<http://www.lmgtfy.com/?q=David+Holmgren>
www.lmgtfy.com
LMGTFY


 Jan Steinman, EcoReality Co-op <http://www.ecoreality.org/> 
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Re: [EVDL] Cheap DC motor control anyone?

[Jan Steinman via EV]

> From: Lee Hart 
> 
> David Chapman via EV wrote:
>> Lee I really appreciate the lead
>> on the GE handbook, I downloaded it and indeed that circuit on pg 293
>> looks perfect for this project…

So, it sounds like one of the goals of the project is to put something together 
from components?

Because I thought Lee’s idea of finding a variable-speed electric drill at a 
thrift store or yard sale was really an excellent idea.

You can probably do so for less than the costs of buying components, especially 
if you’re going to pay “single piece” shipping on them.

And the drill speed control has the advantage of having been designed for motor 
speed control. Newer ones even use pulse-width-modulation, which you can tell 
if it makes a squealing or whistling sound at low speed. That sort of 
controller is going to give you the best low-speed control, with lots more 
torque.

 The more the work is left to nature, the greater the net yield but the 
longer the time required... Thus sometimes the most apparently productive and 
high-yielding sources of energy involve a lot of activity for little return, 
while long-term investments, especially in naturally grown forests, provide the 
greatest value for future generations. -- David Holmgren 

 Jan Steinman, EcoReality Co-op  

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Re: [EVDL] Cheap DC motor control anyone?

[Lee Hart via EV]

David Chapman via EV wrote:

Jan, thanks for the input on this. Lee I really appreciate the lead
on the GE handbook, I downloaded it and indeed that circuit on pg 293
looks perfect for this project...



One question tho, you said something about it needing a capacitor and looking 
at the
schematic I don't see one...


Fig 10.5 is a "quick-n-dirty" circuit that works, but has issues at the 
low-speed end. Have you used a cheap light dimmer, and noticed that the 
brightness is unstable at the dim end of the range? Same thing with that 
circuit; the motor speed will be unstable at the low end.


Look a little farther in the book, at fig. 10.6 and 10.7. These are 
improved circuits that add a 0.2uF capacitor and 2N4987 trigger device.


The 2N4987 is an oddball part from GE that is hard to get today. Newark 
has them for $5.68


http://www.newark.com/nte-electronics/2n4987/t-unilateral-switch/dp/75R9697?CMP=AFC-OP

The 2N4987 is what GE called an SUS. It is really just two transistors 
(one NPN, one PNP, a resistor, and a zener diode). These are all 10 cent 
parts, so you can make it yourself. The GE datasheet shows the circuit.


Or, you can replace it with a modern part. Every manufacturer has a 
different name for it. Common variations are SIDAC or DIAC. I'd try the 
MCC DB3-TP, www.digikey.com DB3-TPMSCT-ND $0.21 each.



Thanks again, I really appreciate you you taking the time to offer
advice. Dach.


You're welcome! Best success with your project. :-)
--
It is vanity to do with more that which can be done with less.
-- William of Ockham
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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Re: [EVDL] Cheap DC motor control anyone?

[David Chapman via EV]

Jan, thanks for the input on this. Lee I really appreciate the lead on the GE 
handbook, I downloaded it and indeed that circuit on pg 293 looks perfect for 
this project;  I am kind of helping / mentoring a friend of one of my sons with 
his project and he doesn't have anything for money so its a fantastic find. 
Looks like we can build it for under 10 bucks and it is simple and will do 
everything he needs it to do so its an "Occamatic" solution. One question tho, 
you said something about it needing a capacitor and looking at the schematic I 
don't see one, in the notes below the drawing (fig. 10.5) it says "A capacitor 
on the arm of R2 is not a cure because there will be no phase shift on the 
reference due  to full wave rectified charging." I wonder if an R/C drain to 
ground between the SCR and C1 might accomplish turning off the SCR quickly? 
Since this is a pm motor I will just leave out the field connection and diode 
piece. BTW, would you just put the 15 amp fuse in the "hot" AC lead before the 
bridge rectifier? Or is there a better place in the circuit? Thanks again, I 
really appreciate you you taking the time to offer advice. Dach. 
  
  

On Wednesday, January 24, 2018 8:17 PM, Lee Hart via EV  
wrote:
 

 Jan Steinman via EV wrote:
> Is this permanent, or temporary/intermittent use?

That's important, because while most treadmill motors have high advertised 
horsepower; in fact, they rarely deliver even a small fraction of that.
>
> I’d put a full-wave bridge rectifier as close to the motor as possible,
> and just call it a 120 VAC motor. Put a standard plug on it. Then you
> could plug it in to a wide variety of AC power control devices, as Lee
> suggests.

Good point! You do have to rectify the AC before it gets to the motor.

> Then, it sounds like a job for a good old-fashioned variac transformer.

That would work great if it can handle the current. Small variacs (rated at a 
few amps) are pretty common and inexpensive used. But ones big enough to handle 
15 amps continuously are quite a bit heavier and more expensive (like 20 lbs 
and 
$100).

> Lee’s ideas will still produce AC, and so would work fine for a universal
> (series-wound) motor, but probably not for a permanent magnet motor

Definitely not for a PM motor. For some reason, I was thinking he had a 
universal motor, which doesn't care whether it's running on AC or DC.

Light dimmers typically use triacs, which are AC devices. But speed controls 
for 
electric drills more often use SCRs, which do have a DC output. The circuits I 
mentioned from the GE SCR manual are all suitable for PM DC motors as well as 
shunt and series motors, because they use SCRs for control. SCRs are better 
suited to inductive loads.

> So, rectify that puppy, and lots more options become available!

Yes. :-)

-- 
It is vanity to do with more that which can be done with less.
        -- William of Ockham
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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Re: [EVDL] Cheap DC motor control anyone?

[Lee Hart via EV]

Jan Steinman via EV wrote:

Is this permanent, or temporary/intermittent use?


That's important, because while most treadmill motors have high advertised 
horsepower; in fact, they rarely deliver even a small fraction of that.


I’d put a full-wave bridge rectifier as close to the motor as possible,
and just call it a 120 VAC motor. Put a standard plug on it. Then you
could plug it in to a wide variety of AC power control devices, as Lee
suggests.


Good point! You do have to rectify the AC before it gets to the motor.


Then, it sounds like a job for a good old-fashioned variac transformer.


That would work great if it can handle the current. Small variacs (rated at a 
few amps) are pretty common and inexpensive used. But ones big enough to handle 
15 amps continuously are quite a bit heavier and more expensive (like 20 lbs and 
$100).



Lee’s ideas will still produce AC, and so would work fine for a universal
(series-wound) motor, but probably not for a permanent magnet motor


Definitely not for a PM motor. For some reason, I was thinking he had a 
universal motor, which doesn't care whether it's running on AC or DC.


Light dimmers typically use triacs, which are AC devices. But speed controls for 
electric drills more often use SCRs, which do have a DC output. The circuits I 
mentioned from the GE SCR manual are all suitable for PM DC motors as well as 
shunt and series motors, because they use SCRs for control. SCRs are better 
suited to inductive loads.



So, rectify that puppy, and lots more options become available!


Yes. :-)

--
It is vanity to do with more that which can be done with less.
-- William of Ockham
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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Re: [EVDL] Cheap DC motor control anyone?

[Jan Steinman via EV]

> Date: Wed, 24 Jan 2018 00:59:48 + (UTC)
> 
> Working on a belt sander project using a 130V PMDC motor off a treadmill. The 
> control board got crushed so I need a simple cheap adjustable speed control. 
> Anyone have something laying around they want to get rid of? Need 115Vac 
> input. Thanks Dach.

Is this permanent, or temporary/intermittent use?

I’d put a full-wave bridge rectifier as close to the motor as possible, and 
just call it a 120 VAC motor. Put a standard plug on it. Then you could plug it 
in to a wide variety of AC power control devices, as Lee suggests.

Then, it sounds like a job for a good old-fashioned variac transformer. They 
aren’t cheap brand new, but you can sometimes find them cheap in surplus or ham 
radio estate sales.

If you don’t intend this to be permanent, you could put your variac in a box 
with a volt meter and a couple standard AC outlets. It can be handy that way 
for so many things.

Lee’s ideas will still produce AC, and so would work fine for a universal 
(series-wound) motor, but probably not for a permanent magnet motor, which will 
just try to go forward and reverse at 60Hz and make a loud hum before it burns 
out.

But if you rectify what goes into your PMDC motor, SCR dimmers should work 
well. Older drills used SCR phase control, but I think newer ones use PWM, 
which will probably make a better speed control than an SCR phase-control will 
— but it will still require rectification for a PM motor.

So, rectify that puppy, and lots more options become available!

 Jan Steinman, EcoReality Co-op 

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Re: [EVDL] Cheap DC motor control anyone?

[Lee Hart via EV]

David Chapman via EV wrote:

Working on a belt sander project using a 130V PMDC motor off a treadmill. The control 
board got crushed so I need a simple cheap adjustable speed control. Anyone have 
something laying around they want to get rid of? Need 115Vac input. Thanks Dach. "Do 
what you can, with what you have, where you are" - Theodore Roosevelt “We reached 
the old wolf in time to watch a fierce green fire dying in her eyes  I was young 
then, and full of trigger-itch; I thought that because fewer wolves meant more deer, that 
no wolves would mean hunters’ paradise. But after seeing the green fire die, I sensed 
that neither the wolf nor the mountain agreed with such a view.” - Aldo Leopold


How about an old-fashioned phase-control light dimmer? It will give you 
variable speed, though not speed "control".


Or, steal the speed control out of an unused or garage-sale 120vac 
drill. The circuit is only slightly more complicated, but uses the 
motor's back-EMF to sort-of regulate the speed.


I'm looking at a circuit in the GE SCR manual 5th edition on page 293. 
It uses a bridge rectifier, 1 SCR, 2 resistors, 1 potentiometer (the 
speed control), 1 capacitor, and two diodes.


--
It is vanity to do with more that which can be done with less.
-- William of Ockham
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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[EVDL] Cheap DC motor control anyone?

[David Chapman via EV]

Working on a belt sander project using a 130V PMDC motor off a treadmill. The 
control board got crushed so I need a simple cheap adjustable speed control. 
Anyone have something laying around they want to get rid of? Need 115Vac input. 
Thanks Dach. "Do what you can, with what you have, where you are" - Theodore 
Roosevelt “We reached the old wolf in time to watch a fierce green fire dying 
in her eyes  I was young then, and full of trigger-itch; I thought that 
because fewer wolves meant more deer, that no wolves would mean hunters’ 
paradise. But after seeing the green fire die, I sensed that neither the wolf 
nor the mountain agreed with such a view.” - Aldo Leopold
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