Rob,
No design effort is needed. The entire circuit is on the EGS002 datasheet that I provided the link to. The hard part is already on the board. The only thing missing from the schematic is the source for the 12V, 5V and rectified/filtered line voltage. For the variable frequency modification, Pin 16 of the EG8010 needs to be disconnected from ground. The top of a 10K pot is connected to 5V, and the bottom to ground. The wiper goes to pin 16. A 0.1uF capacitor should be placed between the wiper and ground to filter noise out of he control circuit. As supplied, pins 18 and 19 of the EG8010 are floating. That sets the output frequency to a range of 0-400Hz. Grounding pin 18 sets the range to 0-100Hz, which is where we want to be. I provided the link to the EG8010 datasheet for education purposes. The chip is impressive, as is the board. The price is mind blowing, considering the performance.
Another feature that I didn't mention is a provision for connecting and LCD display to show the output voltage, output frequency and motor current. This is a direct connection, with no additional circuitry. I didn't mention it because I am somewhat confused as to the exact display that is used, and since I don't intend to use the display, I didn't research it further. If the thermistor/fan is used, the display will also show the temperature.
The power MOSFETs are, without a doubt, overkill for our application in the milliamperes, but when I looked into using smaller devices, I realized that there was no money to be saved, and since this circuit is the basis for 2KW 50 or 60 Hz inverters that work, I thought that there was nothing to be gained by trying to change to smaller parts.
My exact reason for looking at this board was that no design effort, other than laying out a board was needed. After doodling with the layout, I realized that I spent more time at the computer than it would have taken me to hand wire it.
Harvey
I am not an electrical engineer.
I am an electronic hobbyist with a leaning toward ham radio and robotics.
So when I said I would like to see the complete circuit drawn out if you did ever get to build it then
that would be extremely helpful for all of us not quite qualified to design this circuit from the
documentation that you listed.
On 12/18/2016 12:44 AM, Harvey Altstadter hrconsult@... [Homebrew_PCBs] wrote:
Rob,
Although I responded to your post, the information contained in my post was intended to be provided to anyone concerned with modifying a laminator.
The board does exactly what was described in an earlier post where there was a description of using a 555 to drive some other circuitry to provide a PWM output sinewave simulation from a microcontroller. With this board, there is no need to cobble together a clock source, a microcontroller, and various and sundry support components to make then all sing together. As I said, no programming is required, as the EG8010 chip is a dedicated processor that has the firmware built in. I never said that programming a microcontroller is a big deal, but then, in the world that I have worked in, any extra step that doesn't contribute to the end product doesn't get done. In this case, the programming is unnecessary. Some makers don't have tools to load the software into the controller. That could be why some makers buy pre-programmed microcontrollers for their projects. This inexpensive board obviates the need for those tools.
I am not selling anything, either, just providing a piece of information that supports an earlier post, but in a simplified manner.
I understand how the dimmer works. I was selling SCRs and Unijunction transistors (Triacs had not yet been invented) to dimmer manufacturers in the early 1960's while I was in Engineering school. My comment about torque refers to comments made sometime back by users of the Harbor Freight and other laminators that had some problems at slow speed, with standard .062" boards. The use of a variable frequency source allows the motor to function as designed at full torque down to fractional RPM speeds. By calibrating the drive voltage, different speeds can be set for different purposes. Again, with no programming.
As for building the circuit up, I will do so when I have gears for the laminator, or a different laminator. In the current state of my laminator, driving the motor without load will demonstrate that I can change the motor speed, but not tell me anything about the torque. I don't feel that I need to demonstrate that I can change the speed, since using a variable frequency power source is the time tested way of changing the speed of a synchronous motor. When I do complete the construction and testing, I will provide the results here.
Harvey
On 12/17/2016 9:16 PM, Rob roomberg@... [Homebrew_PCBs] wrote:
On 12/17/2016 06:04 PM, Harvey Altstadter hrconsult@... [Homebrew_PCBs] wrote:
..... to which I ask ..... DO I NEED TO CONCERN MYSELF OVER THIS FACT?
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.
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.
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.
On 12/16/2016 09:34 PM, mosaicmerc@... [Homebrew_PCBs] wrote:
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