PWM DC motor circuit?

Steve Taylor · Jul 11, 2004

Al Borowski wrote:

/me points to where I wrote "I already have code for simple things like
PWM"

I saw that, but will Terry "already have code for simple things like PWM"

Steve

Terry Pinnell · Jul 11, 2004

Steve Taylor <steve@ravenfield.com> wrote:

Al Borowski wrote:

/me points to where I wrote "I already have code for simple things like
PWM"

I saw that, but will Terry "already have code for simple things like PWM"

Steve

Definitely not!

--
Terry Pinnell
Hobbyist, West Sussex, UK

Al Borowski · Jul 11, 2004

Steve Taylor wrote:

Al Borowski wrote:

/me points to where I wrote "I already have code for simple things
like PWM"

I saw that, but will Terry "already have code for simple things like PWM"

OK, fair enough.

Al

Steve

John Jardine · Jul 12, 2004

Terry Pinnell <terrypinDELETE@THESEdial.pipex.com> wrote in message
news:c4h2f0pc2dli83km7qcqlfmgakgjbtc5gf@4ax.com...

"John Jardine" <john@jjdesigns.fsnet.co.uk> wrote:
[]
I used to *add* stuff to my cars, rather than take bits away <g>.
Started more than a couple of decades ago on my own cars, when even
basics like windscreen wiper speed control were not always provided.
Later, whenever I got a new company car, I'd have to strip out any
gadgets I'd added. Mind you, as built-in accessories became
increasingly generous, there was less need to add my own projects
anyway. What car now doesn't have a burglar alarm, ice alert,
sidelights-on warning, etc? In fact, it was only as recently as last
week that I got around to adding my very first gadget to my '96 BMW
328SE. It's one of the few things apparently not covered in all modern
cars: what I call a 'Pedestrian Horn'. A footswitch just above my left
foot (the car's auto) initiates a rapid and *relatively* quiet
bip-bip-bip of the horn/siren, to warn little old ladies or horse
riders etc just around the next bend, or that apparently oblivious
driver or passenger emerging from a car ahead. Also has advantage that
I don't need to take hands from steering wheel. The challenge was
access to the horn wiring and getting it inside the car. (Just a low
duty cycle astable driving the existing horn relay.)

Back to curtain motor control. (Can't postpone the admission any
longer!) I'm embarrassed to say that you're quite right, of course.
Don't know what I was thinking. Clearly I should be able to use a
simple single MOSFET or BJT circuit for the PWM speed control, and my
relays/microswitches for F/Off/R control, as you say.

Your post couldn't have been more timely, as I was going to get stuck
in today and build the H-Bridge design I found yesterday in this
month's edition of EPE mag. That's actually a neat design (NPN & PNP
pairs), and incorporates all the facilities I want. But it would have
been time-consuming to biild and test. Thanks for the heads up.

--
Terry Pinnell
Hobbyist, West Sussex, UK

Same here

.
Cars used to be ripe for mod's that the makers now offer as standard. The
last car had a couple of motors and a joystick just to set a wing mirror.
It's crazy the level of technology that can be offered.
I'm a keen DIYer, so years ago realising the cars were becoming a lost
cause, changed tack and pursued home automation projects.
Come the present day and I find the manufacturers have caught up yet again.
No corners seemingly left untouched.
I go down to the Lidl supermarket and buy 'Energy usage analysers' (real and
apparent power, frequency, true RMS Watts, Voltage, current, power factor,
accumulating costs totaliser) for an unbelievable Ł4.99 (last month I bought
another 4!).
They've also sold me sets of 4 beautyfully engineered, remote controlled
(433MHz)power sockets at Ł12. Last week from Aldi's I bought 3 super
quality DVM's at Ł5.99 ea. A radio controlled timepiece? that'll be Ł12 sir.
Battery operated PIR lighting a snip at Ł2.99. Remote garage door opener Ł52
please. The list seems endless.
They won't realise it but the far Eastern manufacturers are ruining my will
to live

.
I bought a Chinese milling machine a couple of years ago. A 1/3 of the UK
price and better quality. It's something I would have enjoyed taking a year
to make homebrew but at that price it was a no-contest.
Don't know about all the other guys here but what I enjoy most is the
'-journey-', the end result (or more likely, not!) is a bit immaterial. I
like to think though before embarking on a pet project, that it has a bit of
a novelty value. If I suspect that there's something already on offer
(cleverer, cheaper, more reliable, more features) then a bit more of that
essential joie de vie, is chipped away.
(Post some pictures of the curtain opener if you complete ).
regards
john

Bob Wilson · Jul 12, 2004

In article
<40f0d75f$0$1298$5a62ac22@per-qv1-newsreader-01.iinet.net.au>,
al.borowski@EraseThis.gmail.com says...

Using a microcontroller to replace a simple quad-comparator-based PWM
circuit
(such as the one mentioned) would seem to be a little silly. Not only
is the uC
more expensive than the comparator, it also requires time spent on
programming
(and debugging). The comparator-based PWM is so simple, that it would
be up and
running before the code for a uP version wer even half finished.

Want to bet on that?

I already have code for simple things like PWM - I'd use a cheap 8 pin
PIC with ADC ($2 AUD in single quantites). The only parts you'd need
would be an 8 pin uC, a pot for PWM adjustment, and the FET and
snubber.

I reakon, if I had the parts on hand, I could get it going in 10
minutes on breadboard. No having to hunt down a quad comparitor or the
needed resistor values - I just have a heap of cheap micro's for
jellybeans when I do things like this.

Already have the code? That's cheating! I could say that I already have
the PWM built up too!

My comment was actually intended for a wider audience, and assumed that
the builder would not just happen to have parts of it (or the code for a
micro) already in existence.

I guess I'm the opposite of you. I don't happen to have a PIC (or its
code) lying around, but I do have tons of LM339s and all standard values
of resistors and caps at my fingertips.

Bob.

John Jardine · Jul 13, 2004

Bob Wilson <rfwilson@send_no_spam.intergate.ca> wrote in message
news:10f41cgkabjg2cf@corp.supernews.com...

In article
40f0d75f$0$1298$5a62ac22@per-qv1-newsreader-01.iinet.net.au>,
al.borowski@EraseThis.gmail.com says...

Using a microcontroller to replace a simple quad-comparator-based PWM
circuit
(such as the one mentioned) would seem to be a little silly. Not only
is the uC
more expensive than the comparator, it also requires time spent on
programming
(and debugging). The comparator-based PWM is so simple, that it would
be up and
running before the code for a uP version wer even half finished.

Want to bet on that?

I already have code for simple things like PWM - I'd use a cheap 8 pin
PIC with ADC ($2 AUD in single quantites). The only parts you'd need
would be an 8 pin uC, a pot for PWM adjustment, and the FET and
snubber.

I reakon, if I had the parts on hand, I could get it going in 10
minutes on breadboard. No having to hunt down a quad comparitor or the
needed resistor values - I just have a heap of cheap micro's for
jellybeans when I do things like this.

Already have the code? That's cheating! I could say that I already have
the PWM built up too!

My comment was actually intended for a wider audience, and assumed that
the builder would not just happen to have parts of it (or the code for a
micro) already in existence.

I guess I'm the opposite of you. I don't happen to have a PIC (or its
code) lying around, but I do have tons of LM339s and all standard values
of resistors and caps at my fingertips.

Bob.

Good point.

Have just redesigned 3 small low cost gp 'timer-switch' type sm PCB products
(costs equiv to 2 USD ). Minimum cost was the design target. 2 of the
existing designs used PICs. It proved 25% cheaper (and a better spec') to
redesign just using discretes. (I do have PICs and code snippets to call on
if a job warrants it).
The PICs are not a general panacea and I've seen more than a couple of
occasions where PICs had been badly used because their programmers clearly
didn't understand the analogue stuff (to my benefit of course

.
regards
john

Gordon Youd · Jul 15, 2004

Terry,
MFACOMO DRILLS sell a PWM module which allows infinitely variable motor RPM
to be set.

About 1 inch cube, 2 wires in, 2 wires out with a screw to set the speed.

Rapid electronics also sell them, they are about Ł8.00.

Hope this helps.

Regards, Gordon.

----------------------------------------------------------------------------
-------------
"Terry Pinnell" <terrypinDELETE@THESEdial.pipex.com> wrote in message
news:badve05nj0avdhtq06qipbn7sd1mipp9hu@4ax.com...

Could someone kindly save me a bit of time in finding a suitable
circuit for driving a DC motor with PWM please? My first hour of
googling has found many threads, but so far no specific relevant
schematics.

The DC motor is from a cordless screwdriver, used originally with two
NiCad C cells, and duly marked as '2.4V'. I ran it briefly at 5V and
assume it would tolerate that, giving me higher torque potential. It's
geared, and (unloaded with 2.4V applied) gives 250 rpm. That's too
fast for my curtain control application so I want to be able to reduce
it. Hence PWM.

I'll probably use limit switches and a C/O relay for the
forward/reverse/off control, at least while getting the challenging
mechanicals sorted (as per separate thread). So I don't need to
consider the complications of combining PWM with an H-Bridge.

My first thoughts are to use a 5V supply (derived from a convenient
fairly heavy duty 12V supply I have nearby) with a variable duty cycle
555 (or maybe a 4001/4011 equivalent), directly driving a medium power
MOSFET, with the motor between its drain and 5V. I'll breadboard that
shortly, but meanwhile:
- will that simple approach be reliable?
- any snags or protective measures to watch out for?
- is there an 'optimum' frequency range?
- if I designed a *high* duty cycle from 555, which I recall makes it
easier to achieve a wide d/c range, what is most efficient way to
configure the output MOSFET stage?
- I happen to have a 2N3055 (or similar) already neatly mounted on a
h/sink, from a previous project; any major reason why I shouldn't use
that instead of a MOSFET?

As mentioned in the curtain thread, I'd like to build this asap, as
the full-speed motor action is adding to my design and testing
problems.

TIA.

--
Terry Pinnell
Hobbyist, West Sussex, UK

Terry Pinnell · Jul 15, 2004

"Gordon Youd" <gordon@Zgyoud.demon.co.uk> wrote:

Terry,
MFACOMO DRILLS sell a PWM module which allows infinitely variable motor RPM
to be set.

About 1 inch cube, 2 wires in, 2 wires out with a screw to set the speed.

Rapid electronics also sell them, they are about Ł8.00.

Hope this helps.

Thanks, Gordon. I'll take a look at that. However, at the moment, it's
looking just possible that I can get away with the raw supply. I'm
using the original 2.4 V and under the load of the curtain it's a
manageable speed.

--
Terry Pinnell
Hobbyist, West Sussex, UK

----------------------------------------------------------------------------
-------------
"Terry Pinnell" <terrypinDELETE@THESEdial.pipex.com> wrote in message
news:badve05nj0avdhtq06qipbn7sd1mipp9hu@4ax.com...
Could someone kindly save me a bit of time in finding a suitable
circuit for driving a DC motor with PWM please? My first hour of
googling has found many threads, but so far no specific relevant
schematics.

The DC motor is from a cordless screwdriver, used originally with two
NiCad C cells, and duly marked as '2.4V'. I ran it briefly at 5V and
assume it would tolerate that, giving me higher torque potential. It's
geared, and (unloaded with 2.4V applied) gives 250 rpm. That's too
fast for my curtain control application so I want to be able to reduce
it. Hence PWM.

I'll probably use limit switches and a C/O relay for the
forward/reverse/off control, at least while getting the challenging
mechanicals sorted (as per separate thread). So I don't need to
consider the complications of combining PWM with an H-Bridge.

My first thoughts are to use a 5V supply (derived from a convenient
fairly heavy duty 12V supply I have nearby) with a variable duty cycle
555 (or maybe a 4001/4011 equivalent), directly driving a medium power
MOSFET, with the motor between its drain and 5V. I'll breadboard that
shortly, but meanwhile:
- will that simple approach be reliable?
- any snags or protective measures to watch out for?
- is there an 'optimum' frequency range?
- if I designed a *high* duty cycle from 555, which I recall makes it
easier to achieve a wide d/c range, what is most efficient way to
configure the output MOSFET stage?
- I happen to have a 2N3055 (or similar) already neatly mounted on a
h/sink, from a previous project; any major reason why I shouldn't use
that instead of a MOSFET?

As mentioned in the curtain thread, I'd like to build this asap, as
the full-speed motor action is adding to my design and testing
problems.

TIA.

--
Terry Pinnell
Hobbyist, West Sussex, UK

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Ron M. · Oct 31, 2015

On Saturday, July 10, 2004 at 1:19:24 PM UTC-5, Terry Pinnell wrote:

"John Jardine" <john@jjdesigns.fsnet.co.uk> wrote:

Terry Pinnell <terrypinDELETE@THESEdial.pipex.com> wrote in message
news:badve05nj0avdhtq06qipbn7sd1mipp9hu@4ax.com...
[clp]
Terry Pinnell
Hobbyist, West Sussex, UK

My cooker extracter uses a pot', setting a 555 pwm, driving a TIP110
darlington, directly feeding an ex Alfa-Romeo radiator fan. Frequency is
arbitrary at a couple of kHz. No heatsinking, no protection or
jiggery-pokery parts, other than a diode across the motor.
There must be all of 50p's worth of bits and it's run fine for years.
regards
john

Thanks. I'm probably going to have to get a bit more complex in this
case, due to a combination of the reversal requirement plus automatic
stopping at each extreme. In considering that very simple '555 driving
MOSFET' appoach, (or the epanorama site version), I'd vaguely thought
I could implement these additional facilities with a relay and
microswitches. But of course that's not possible; the motor will be
permanently connected with one specific polarity, one end to Vcc and
the other via the MOSFET (or NPN BJT) to ground.

However, I might *still* build such a simple PWM circuit, purely to
get the speed down while I experiment. At present, I barely get time
to apply power before the cord flies off the pulley or fouls up in
some way!

But for my final circuit, it now looks as if I'll need an H-Bridge
approach. That looks more easily done with two NPN and two PNP BJTs,
but I'd welcome others' views please.

How's the Alfa getting on without its fan?

--
Terry Pinnell
Hobbyist, West Sussex, UK

Use relay for reverse,556 based PWM for speed/power control and 555 timers to drive it all. Doing something similar with linear actuator on a gate closer. Limits can be either direct in line with motor(diode steered) and/or sensed from across those switches via bridge rectifier for secondary limit (opto-isolated).

Ron M. · Oct 31, 2015

On Saturday, October 31, 2015 at 1:57:45 PM UTC-5, Ron M. wrote:

On Saturday, July 10, 2004 at 1:19:24 PM UTC-5, Terry Pinnell wrote:
"John Jardine" <john@jjdesigns.fsnet.co.uk> wrote:

Terry Pinnell <terrypinDELETE@THESEdial.pipex.com> wrote in message
news:badve05nj0avdhtq06qipbn7sd1mipp9hu@4ax.com...
[clp]
Terry Pinnell
Hobbyist, West Sussex, UK

My cooker extracter uses a pot', setting a 555 pwm, driving a TIP110
darlington, directly feeding an ex Alfa-Romeo radiator fan. Frequency is
arbitrary at a couple of kHz. No heatsinking, no protection or
jiggery-pokery parts, other than a diode across the motor.
There must be all of 50p's worth of bits and it's run fine for years.
regards
john

Thanks. I'm probably going to have to get a bit more complex in this
case, due to a combination of the reversal requirement plus automatic
stopping at each extreme. In considering that very simple '555 driving
MOSFET' appoach, (or the epanorama site version), I'd vaguely thought
I could implement these additional facilities with a relay and
microswitches. But of course that's not possible; the motor will be
permanently connected with one specific polarity, one end to Vcc and
the other via the MOSFET (or NPN BJT) to ground.

However, I might *still* build such a simple PWM circuit, purely to
get the speed down while I experiment. At present, I barely get time
to apply power before the cord flies off the pulley or fouls up in
some way!

But for my final circuit, it now looks as if I'll need an H-Bridge
approach. That looks more easily done with two NPN and two PNP BJTs,
but I'd welcome others' views please.

How's the Alfa getting on without its fan?

--
Terry Pinnell
Hobbyist, West Sussex, UK

Use relay for reverse,556 based PWM for speed/power control and 555 timers to drive it all. Doing something similar with linear actuator on a gate closer. Limits can be either direct in line with motor(diode steered) and/or sensed from across those switches via bridge rectifier for secondary limit (opto-isolated).

DPDT for reverse. Also time limits of timers are a 3rd limit to consider. Google linear actuator limit switch for diagrams of wiring. Just 2 switches and 2 diodes. Here is the link I used.

http://www.progressiveautomations.com/images/pdf/Limit_Switch_Wiring_Diagram.pdf

It shows limit in only one direction but simply needs another switch and diode for other direction. Good luck.

Tim Wescott · Nov 1, 2015

On Sat, 31 Oct 2015 11:57:40 -0700, Ron M. wrote:

On Saturday, July 10, 2004 at 1:19:24 PM UTC-5, Terry Pinnell wrote:
"John Jardine" <john@jjdesigns.fsnet.co.uk> wrote:

Terry Pinnell <terrypinDELETE@THESEdial.pipex.com> wrote in message
news:badve05nj0avdhtq06qipbn7sd1mipp9hu@4ax.com...
[clp]
Terry Pinnell Hobbyist, West Sussex, UK

My cooker extracter uses a pot', setting a 555 pwm, driving a TIP110
darlington, directly feeding an ex Alfa-Romeo radiator fan. Frequency
is arbitrary at a couple of kHz. No heatsinking, no protection or
jiggery-pokery parts, other than a diode across the motor.
There must be all of 50p's worth of bits and it's run fine for years.
regards john

Thanks. I'm probably going to have to get a bit more complex in this
case, due to a combination of the reversal requirement plus automatic
stopping at each extreme. In considering that very simple '555 driving
MOSFET' appoach, (or the epanorama site version), I'd vaguely thought I
could implement these additional facilities with a relay and
microswitches. But of course that's not possible; the motor will be
permanently connected with one specific polarity, one end to Vcc and
the other via the MOSFET (or NPN BJT) to ground.

However, I might *still* build such a simple PWM circuit, purely to get
the speed down while I experiment. At present, I barely get time to
apply power before the cord flies off the pulley or fouls up in some
way!

But for my final circuit, it now looks as if I'll need an H-Bridge
approach. That looks more easily done with two NPN and two PNP BJTs,
but I'd welcome others' views please.

How's the Alfa getting on without its fan?

--
Terry Pinnell Hobbyist, West Sussex, UK

Use relay for reverse,556 based PWM for speed/power control and 555
timers to drive it all. Doing something similar with linear actuator on
a gate closer. Limits can be either direct in line with motor(diode
steered) and/or sensed from across those switches via bridge rectifier
for secondary limit (opto-isolated).

An 11 year old thread has been revived by some slimeball sales guy, and
you respond.

Hmm.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Ron M. · Nov 1, 2015

On Saturday, October 31, 2015 at 4:01:47 PM UTC-5, Tim Wescott wrote:

On Sat, 31 Oct 2015 11:57:40 -0700, Ron M. wrote:

On Saturday, July 10, 2004 at 1:19:24 PM UTC-5, Terry Pinnell wrote:
"John Jardine" <john@jjdesigns.fsnet.co.uk> wrote:

Terry Pinnell <terrypinDELETE@THESEdial.pipex.com> wrote in message
news:badve05nj0avdhtq06qipbn7sd1mipp9hu@4ax.com...
[clp]
Terry Pinnell Hobbyist, West Sussex, UK

My cooker extracter uses a pot', setting a 555 pwm, driving a TIP110
darlington, directly feeding an ex Alfa-Romeo radiator fan. Frequency
is arbitrary at a couple of kHz. No heatsinking, no protection or
jiggery-pokery parts, other than a diode across the motor.
There must be all of 50p's worth of bits and it's run fine for years.
regards john

Thanks. I'm probably going to have to get a bit more complex in this
case, due to a combination of the reversal requirement plus automatic
stopping at each extreme. In considering that very simple '555 driving
MOSFET' appoach, (or the epanorama site version), I'd vaguely thought I
could implement these additional facilities with a relay and
microswitches. But of course that's not possible; the motor will be
permanently connected with one specific polarity, one end to Vcc and
the other via the MOSFET (or NPN BJT) to ground.

However, I might *still* build such a simple PWM circuit, purely to get
the speed down while I experiment. At present, I barely get time to
apply power before the cord flies off the pulley or fouls up in some
way!

But for my final circuit, it now looks as if I'll need an H-Bridge
approach. That looks more easily done with two NPN and two PNP BJTs,
but I'd welcome others' views please.

How's the Alfa getting on without its fan?

--
Terry Pinnell Hobbyist, West Sussex, UK

Use relay for reverse,556 based PWM for speed/power control and 555
timers to drive it all. Doing something similar with linear actuator on
a gate closer. Limits can be either direct in line with motor(diode
steered) and/or sensed from across those switches via bridge rectifier
for secondary limit (opto-isolated).

An 11 year old thread has been revived by some slimeball sales guy, and
you respond.

Hmm.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Sorry. Missed the date on the OP. My bad.

Tim Wescott · Nov 2, 2015

On Sun, 01 Nov 2015 13:38:38 -0800, Ron M. wrote:

On Saturday, October 31, 2015 at 4:01:47 PM UTC-5, Tim Wescott wrote:
On Sat, 31 Oct 2015 11:57:40 -0700, Ron M. wrote:

On Saturday, July 10, 2004 at 1:19:24 PM UTC-5, Terry Pinnell wrote:
"John Jardine" <john@jjdesigns.fsnet.co.uk> wrote:

Terry Pinnell <terrypinDELETE@THESEdial.pipex.com> wrote in message
news:badve05nj0avdhtq06qipbn7sd1mipp9hu@4ax.com...
[clp]
Terry Pinnell Hobbyist, West Sussex, UK

My cooker extracter uses a pot', setting a 555 pwm, driving a
TIP110 darlington, directly feeding an ex Alfa-Romeo radiator fan.
Frequency is arbitrary at a couple of kHz. No heatsinking, no
protection or jiggery-pokery parts, other than a diode across the
motor.
There must be all of 50p's worth of bits and it's run fine for
years. regards john

Thanks. I'm probably going to have to get a bit more complex in this
case, due to a combination of the reversal requirement plus
automatic stopping at each extreme. In considering that very simple
'555 driving MOSFET' appoach, (or the epanorama site version), I'd
vaguely thought I could implement these additional facilities with a
relay and microswitches. But of course that's not possible; the
motor will be permanently connected with one specific polarity, one
end to Vcc and the other via the MOSFET (or NPN BJT) to ground.

However, I might *still* build such a simple PWM circuit, purely to
get the speed down while I experiment. At present, I barely get time
to apply power before the cord flies off the pulley or fouls up in
some way!

But for my final circuit, it now looks as if I'll need an H-Bridge
approach. That looks more easily done with two NPN and two PNP BJTs,
but I'd welcome others' views please.

How's the Alfa getting on without its fan?

--
Terry Pinnell Hobbyist, West Sussex, UK

Use relay for reverse,556 based PWM for speed/power control and 555
timers to drive it all. Doing something similar with linear actuator
on a gate closer. Limits can be either direct in line with
motor(diode steered) and/or sensed from across those switches via
bridge rectifier for secondary limit (opto-isolated).

An 11 year old thread has been revived by some slimeball sales guy, and
you respond.

Hmm.

--

Tim Wescott Wescott Design Services http://www.wescottdesign.com

Sorry. Missed the date on the OP. My bad.

I shouldn't net cop that stuff, but the threads coming back to life tend
to tweak me one way or another.

Zombie threads, shuffling along with green skin and dead eyes...

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Ron M. · Nov 5, 2015

On Sunday, November 1, 2015 at 5:05:45 PM UTC-6, Tim Wescott wrote:

On Sun, 01 Nov 2015 13:38:38 -0800, Ron M. wrote:

On Saturday, October 31, 2015 at 4:01:47 PM UTC-5, Tim Wescott wrote:
On Sat, 31 Oct 2015 11:57:40 -0700, Ron M. wrote:

On Saturday, July 10, 2004 at 1:19:24 PM UTC-5, Terry Pinnell wrote:
"John Jardine" <john@jjdesigns.fsnet.co.uk> wrote:

Terry Pinnell <terrypinDELETE@THESEdial.pipex.com> wrote in message
news:badve05nj0avdhtq06qipbn7sd1mipp9hu@4ax.com...
[clp]
Terry Pinnell Hobbyist, West Sussex, UK

My cooker extracter uses a pot', setting a 555 pwm, driving a
TIP110 darlington, directly feeding an ex Alfa-Romeo radiator fan.
Frequency is arbitrary at a couple of kHz. No heatsinking, no
protection or jiggery-pokery parts, other than a diode across the
motor.
There must be all of 50p's worth of bits and it's run fine for
years. regards john

Thanks. I'm probably going to have to get a bit more complex in this
case, due to a combination of the reversal requirement plus
automatic stopping at each extreme. In considering that very simple
'555 driving MOSFET' appoach, (or the epanorama site version), I'd
vaguely thought I could implement these additional facilities with a
relay and microswitches. But of course that's not possible; the
motor will be permanently connected with one specific polarity, one
end to Vcc and the other via the MOSFET (or NPN BJT) to ground.

However, I might *still* build such a simple PWM circuit, purely to
get the speed down while I experiment. At present, I barely get time
to apply power before the cord flies off the pulley or fouls up in
some way!

But for my final circuit, it now looks as if I'll need an H-Bridge
approach. That looks more easily done with two NPN and two PNP BJTs,
but I'd welcome others' views please.

How's the Alfa getting on without its fan?

--
Terry Pinnell Hobbyist, West Sussex, UK

Use relay for reverse,556 based PWM for speed/power control and 555
timers to drive it all. Doing something similar with linear actuator
on a gate closer. Limits can be either direct in line with
motor(diode steered) and/or sensed from across those switches via
bridge rectifier for secondary limit (opto-isolated).

An 11 year old thread has been revived by some slimeball sales guy, and
you respond.

Hmm.

--

Tim Wescott Wescott Design Services http://www.wescottdesign.com

Sorry. Missed the date on the OP. My bad.

I shouldn't net cop that stuff, but the threads coming back to life tend
to tweak me one way or another.

Zombie threads, shuffling along with green skin and dead eyes...

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

I know Tim. I have a tendency to be overly helpful sometimes and missed the date totally in my zeal.

Phil Hobbs · Nov 6, 2015

On 11/05/2015 02:12 PM, Ron M. wrote:

On Sunday, November 1, 2015 at 5:05:45 PM UTC-6, Tim Wescott wrote:
On Sun, 01 Nov 2015 13:38:38 -0800, Ron M. wrote:

On Saturday, October 31, 2015 at 4:01:47 PM UTC-5, Tim Wescott wrote:
On Sat, 31 Oct 2015 11:57:40 -0700, Ron M. wrote:

On Saturday, July 10, 2004 at 1:19:24 PM UTC-5, Terry Pinnell wrote:
"John Jardine" <john@jjdesigns.fsnet.co.uk> wrote:

Terry Pinnell <terrypinDELETE@THESEdial.pipex.com> wrote in message
news:badve05nj0avdhtq06qipbn7sd1mipp9hu@4ax.com...
[clp]
Terry Pinnell Hobbyist, West Sussex, UK

My cooker extracter uses a pot', setting a 555 pwm, driving a
TIP110 darlington, directly feeding an ex Alfa-Romeo radiator fan.
Frequency is arbitrary at a couple of kHz. No heatsinking, no
protection or jiggery-pokery parts, other than a diode across the
motor.
There must be all of 50p's worth of bits and it's run fine for
years. regards john

Thanks. I'm probably going to have to get a bit more complex in this
case, due to a combination of the reversal requirement plus
automatic stopping at each extreme. In considering that very simple
'555 driving MOSFET' appoach, (or the epanorama site version), I'd
vaguely thought I could implement these additional facilities with a
relay and microswitches. But of course that's not possible; the
motor will be permanently connected with one specific polarity, one
end to Vcc and the other via the MOSFET (or NPN BJT) to ground.

However, I might *still* build such a simple PWM circuit, purely to
get the speed down while I experiment. At present, I barely get time
to apply power before the cord flies off the pulley or fouls up in
some way!

But for my final circuit, it now looks as if I'll need an H-Bridge
approach. That looks more easily done with two NPN and two PNP BJTs,
but I'd welcome others' views please.

How's the Alfa getting on without its fan?

--
Terry Pinnell Hobbyist, West Sussex, UK

Use relay for reverse,556 based PWM for speed/power control and 555
timers to drive it all. Doing something similar with linear actuator
on a gate closer. Limits can be either direct in line with
motor(diode steered) and/or sensed from across those switches via
bridge rectifier for secondary limit (opto-isolated).

An 11 year old thread has been revived by some slimeball sales guy, and
you respond.

Hmm.

--

Tim Wescott Wescott Design Services http://www.wescottdesign.com

Sorry. Missed the date on the OP. My bad.

I shouldn't net cop that stuff, but the threads coming back to life tend
to tweak me one way or another.

Zombie threads, shuffling along with green skin and dead eyes...

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

I know Tim. I have a tendency to be overly helpful sometimes and missed the date totally in my zeal.

Ah, no worries. Probably few noobs read the archives, so it's good to
go over stuff periodically. People have been rediscovering and
republishing the results of some of my early papers lately.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

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