On 12/17/2016 06:04 PM, Harvey
Altstadter
hrconsult@...
[Homebrew_PCBs] wrote:
Rob,
The advantage of using a variable frequency supply at
full voltage is that the motor retains it's torque
characteristics all the way down in speed.
..... to which I ask ..... DO I NEED TO CONCERN MYSELF OVER
THIS FACT?
Please do enlighten me as to how this torque characteristic
means anything to my and my task at hand which is to take
this synchronous motor..:
http://www.learnmorsecode.com/laminator/slowmotor.jpg
which humps a minuscule 31 mA when it turns the gears with
enough force to pinch and push a board through the
rollers.
Perhaps I am missing something VERY important here.
Please do tell me what that is.
I see no advantage to utilizing this particular EGS002
circuit board over what I have already
research and documented.
UNLESS
and this can be a big issue for a lot of DIY hackers.....
unless the the issue is what you said here... BUT NO
PROGRAMMING IS REQUIRED
If the fact that no progamming is required is the reason for
using it then sure......
do it up....
but I would REALLY like to see you build one of these and
show us how its done.
I am a retired computer programmer with ailing vision.
I won't be reading the "formidable" datasheet.
Now for those of you unable to program a microcontroller
for hacking motor speed control for ANY model of ANY
laminator to attain single pass toner transfer......
I'm not selling anything here.
I'm just sharing how to do something dirt cheap.
I am from the school of thought that I should learn each and
every component of anything I build
so I avoid using single board computers like ARDUINO and
raspberry PI and stick do the most basic
of microcontrollers.... the PIC16F628A
If you want to put some smarts into some kind of
hardware.......
you use a microcontroller to make a machine smart....give it
a BRAIN.
So when I want a machine to DO something IF a sensor has a
specific value
I don't try to figure out a discrete component circuit.
I use a microcontroller that makes decisions.
IF you want to read a thermister... get its resistance
value... then turn on or off a heater.......
then you need nothing more than one GPIO pin for the
thermister and one GPIO pin for the output
to turn on an LED circuit.
THAT LED circuit is inside a MOC3020 which fires a low power
triac that fires a high power triac
which can control ANY heating element you ever will own....
from a hot plate to a clothes dryer.
And a clone of that output circuit is used to turn on the
roller motor.
So then you say its a big deal to program a microcontroller.
Maybe if you are using assembler or C language.
Check out micro engineering labs
http://store.melabs.com/cat/PBP.html
PicBasic BASIC programming language for Microchip's PIC
microcontrollers.
Noting that they have a free version that was distributed
with a Chuck Hellebuyck book
that has a 31 line limit.
http://pbp3.com/download.html
You can easily do a heat or motor control program even with
31 lines limit.
PicBasic compiles into a HEX file and then you burn that HEX
file into a PIC16F628A chip.
Burners are dirts cheap now...$6... $12...$20..... for K150
.... PicKit3..... all sorts of cheap stuff out there.....
so if you want to get a brain for you DIY hacked toys......
perhaps you want to play with BASIC.
A very simple way to get variable frequency AC
power to control the motor can be purchased for
less that US $6.00 on e-bay. To that needs to be
added some simple circuitry, but no programming is
required.
http://www.ebay.com/itm/EGS002-Pure-Sine-Wave-Inverter-Drive-Board-SPWM-EG8010-IR2110-for-128-32-LCD-/162237452451?hash=item25c61b10a3:g:OrAAAOSwNRdX5PgN
This is billed as an inverter driver board. It is
sold as a fixed frequency device, but the chip is
capable of doing wonderful things. By setting a
jumper and lifting one pin, and inserting a pot,
the board becomes a variable frequency driver. All
that is needed to be added is an H-Bridge circuit,
and a source of 5V and 12 Volts, and a
rectifier/filter for the incoming line voltage. An
isolated 12V wall wart and a three terminal 5V
regulator will do just fine.
The datasheet/user manual for the board is here:
http://www.egmicro.com/download/EGS002_manual_en.pdf
The schematic on the board datasheet already
shows the board connected to the H-Bridge.
(Everything to the right of the number blocks) For
the low currents involved here, the fan,
thermistor and driver transistor are not needed,
and if you use the specified MOSFETS, you
shouldn't need heatsinks. The value of L1 was left
off the schematic, and is 3.3 mH. It has to be
capable of carrying the motor current.
The datasheet for the EG8010 frequency control
chip has the information for making the device a
variable frequency generator. The datasheet, here:
https://www.google.com/search?q=EG8010&ie=utf-8&oe=utf-8
is formidable, but the only information necessary
is in a paragraph and diagram that starts on page
15 and continues onto page 16.
The parts for the H-Bridge are very inexpensive.
The MOSFETS are available on e-bay for as little
as 5 for US $0.99.
I started to layout a PWB for the bridge, but put
it on hold when I did, what apparently others have
done, by melting a gear in my Harbor Freight
laminator while testing out my temperature
controller. The circuit is so simple, that it
should be easy enough to build by hand wiring. The
schematic shows the circuit working on 400 VDC
with an output voltage of 220VAC, but that voltage
is the supply for the motor only, and it looks
like it will work on any voltage, including fairly
low voltages. The pot in the bridge circuit
adjusts the actual output voltage.
This brings me to the usual reminder and
warning about not working with these voltages
unless you really know what you are doing, and
are comfortable doing the work. Line voltages
are killers, so beware. The output voltage of
this circuit is not referenced to the mains
ground, so connecting it there should lead to a
nasty surprise involving the release of the
magic smoke.
Harvey
On 12/16/2016 8:20 PM,
Rob
roomberg@...
[Homebrew_PCBs] wrote:
ANY hacking of ANY
electrical appliance can lead to plastic
meltdowns or fire.
That is the nature of hacking.
You don't even think of walking away from
one of these before it cools off.
If you do then thats on you.
AND
since I did succesfully raise the
temperature without melting plastic
structures
I concluded it would be feasible if the
nylon plastic gears were replaced with metal
gears.
I ruined ONE nylon gear running heaters at
390 degrees.
I would not have let the heater go above 350
if it had not been for the question of
COULD we use the 370 degree BROTHER toner
...not just 340 degree HP toner.
And as far as speed control goes.......
I didn't sprinkle any spice on a 555 to make
PWM.
I just told the MOC3020/BTA24 triac circuit
hanging off a PIC16F628 pin to stop...wait a
few seconds...then
go. I figured I already had triac heater
control so it was simple enough to control
the motor.
All parts ...soup to nuts cost about $12 for
heater and motor control by one PIC16F628
with an LCD
to keep track of settings.
http://www.learnmorsecode.com/laminator/pic/index.html
Noting the pictures show the hot press and
not the laminator in use.
The only doubt I have about that approach
is that tampering with the heating
mechanism to push temps above design
specs. can lead to plastic meltdowns, and
possibly a fire.
Slowing the rollers however is a different
matter as it doesn't risk exceeding the
device specs without added protections.
Since you raised the point I gave it some
thought and even did a small LTspice sim.
It would appear that rectifying the 120VAC
into DC (like a PC SMPS or cellular phone
charger) and then producing a stepped
replica of a sine wave using scaled PWM
fed into a 220 uF or larger cap (as also
found in PC SMPS units): we can have a
variable frequency sinewave suitable for
altering the speed of a <200mA
synchronous AC motor without risk of a
breakdown or fire.
The caveat here is we're dealing with the
120VAC side of things and must design
appropriately.
Now to drive the sine wave PWM...a 555
chip can do it via an optocoupler into t
he high voltgae FET (also found in a PC
SMPS)
This is it in principle, but not
exactly,as we'd need a variable freq sine
wave source perhaps from 10Hz to 60hz.
Generating
PWM from rectified sine wave using 555