What is the IC, the orange arrow is pointing too? I cannot make out the number on it.
The heat sink contains the switching MOSFETs. These are the “transistors” that take their signal from the timing circuit. They are low voltage, high current, solid state switches. They do not behave like a traditional transistor, in the sense that they do not spend any time in the transition state. They are either open or closed.
Check them if the inverter does not function. They cannot handle having the battery hooked up backwards.
I am pretty sure you have a modified sine wave inverter, which is a pwm circuit. I suppose the goal is to simply speed up the cycles and change the duty cycle.
Look for a 555 timer ic somewhere on the board.
IF it is a 555 the arrow is pointing too, there are two blue resistors above the transformer, but to the left of it looks like a square variable resistor with a screw top… 555s adjust their frequency with the resistor values, so that might adjust the frequency especially between 50hz and 60hz. But you are right, you need to know that chip number the arrow is pointing to. And really you want to look at the signal with a scope.
Here’s the problem with that Mike. Unless you are ambidextrous you end up with one arm way bigger than the other, like if popeye only had half a can of spinach and it all went to one arm… It would mean getting your shirts all specially tailored and possibly having to walk around bent to one side because of being out of balance.
Even If I owned a decent chainsaw, for small jobs, I would still grab the Corona saw and my wheelbarrow and get it done. Very well designed, like Kristijan’s Vejnik hand axe.
PS I wear stretchy shirts!
I have a folding corona pruning saw that I keep around just for the little jobs. Anything bigger than what my loppers can handle and too annoying to break out the chainsaw.
It’s hard to see what’s going on from the pictures, but based on the size of the outlets, these are small inverters, a few hundred watts. As Bruce Jackson said, most likely modified sine wave, which really means modified square wave. The transformer is part of a DC to DC converter. It produces something over 120 volts, DC. This converter runs at a frequency well above 60 Hz, so the transformer is smaller and therefore cheaper. Transformers are the highest-cost parts in an inverter, so this is important. After the DC to DC converter, there will be four, or a multiple of four, mosfets that will connect the high voltage DC to the inverter output, first in one polarity, then in the opposite. These are square, fast rise time pulses, like a square wave, but with a delay between pulses. The delay reduces the harmonic distortion (but not much) compared to a regular square wave, so it’s called modified sine wave (poor description, but good advertising). You may be able to increase the DC to DC converter output voltage, which will increase the inverter output voltage. At some point the output switching mosfets will no longer handle the higher voltage.
If you want higher frequency (which you probably don’t with your particular saw), there will be a microcontroller or more likely a special purpose IC that handles the oscillator and mosfet switching logic. You may be able to increase the frequency once you figure out how the designers did whatever they did.
The back-side of the inverter from the previous photo with the brown circuit board. The back side of that board is green.
The white arrow points to a micro-controller labeled 34063 HTNJP
The black arrows point to a pair of micro-controllers that have their designations removed. They could be KA3525A.
On the other side of this circuit board (pictured in previous post):
The orange arrow points to a micro-controller labeled RX3152 10450036
And, there are six total MOSFETS:
two on the 12V side labeled SSPL5508
four on the 120V side labeled JCS64OC
You can see an indentation on the rotor core, and a pair of green wires from the case to the stator coils.
The brushes on top of the stator are not visible in this photo. They contact the rotor winding via the copper plates on top of the rotor in the photo.
I know it might be crazy but I would try 10 car batteries in series to power the saw. Or ten little 12ah ups batteries. That’s a DC brush motor.
My SA200 Lincoln welder has a 120dc plug and the side grinder runs with great power when I use that.
This way should be more efficient, as you are not losing power in an inverter.
If it had a permanent magnet for the field, it would be DC-only. With the wound field, either AC or DC will work. When the AC voltage reverses, the armature magnetic field reverses, but so does the field winding magnetic field, so the motor keeps on keeping on in the same direction.
I’m interested in how your grinder runs on batteries. The armature current (and voltage) is already changing faster than the 60 Hz line voltage, but straight DC to the field may behave a little different because of the inductance of the winding. Or maybe not
It will also be interesting to see what happens to the switch. DC current, high voltage, and a series inductor is the classic way to produce an arc. Or even low voltage:
I remember my grandfather and uncle had electric drills labeled for 110 V AC/DC. They had serious trigger switch pull. When I was little, there was one I couldn’t pull hard enough to turn on. Likely big contacts and fast snap-action to handle the DC. Oh, maybe little fingers.
JoePA,
I am posting this way down in the exchange now; hopefully linked back to your original premise of powering an electric chainsaw " . . . to use it in the field off of a 12V battery . . ."
No matter how I do the maths I get you will be discharging that 12 volt battery at 122 amps with a loaded working chainsaw. 2500 watts. There is your 5 horsepower gasoline saw.
I actually do have decades of a variety of professional expreineces with just how much winch motors; tarp pulling motors, sails lifting motors, and many others being 12volt battery powered will suck down the batteries.
You do not seem to have this awarenesss.
Here is a short Minn Kota video about trolling motor portable batteries selection. These trolling motors would only suck down a 12V battery at less than half the power draw your electric chainsaw will.
I do own and have used a commercially made permanent magnet 12Vdc chains saw lightly in hunting vehicles since 1979. It was intended for 10% duty cycling at best.
Use the presenters site link in this Minn Kota video to view out many more references on a 12Vdc batteries available power, versus use, versus time:
I am not going to try and educate these relationships gained over decades of usages. Battery life’s shortened, overworking them. Motors overheated and burnt out. Motors over-volt’ed over-sped (hopper-jumper cars), the fixing epoxy heat weaken and then the armatures spinning out their copper windings into a hair-ball lock-up. Actual copper commutator bars in the armatures melted into running globs. The never-forget eyes watering acrid stench of burnt varnish’s, shellacks, epoxy.
BIG, heavy 12Vdc batteries and banked batteries can, and will do all of this.
Just like NOx’ing continuously an IC engine. Forced jack up power shortens Life.
Read away man. Cheaper to learn this way, believe me.
Steve Unruh
It is a voltage regulator for 1.5a for buck/boost applications. Chances are it is what feeds the low voltage side of the circuit.
I dont think that is right. Ka3525a is a 16 pin package, and that only has 14 pins (7 on each side) unless two pins were clipped or I counted wrong both happen.
If it IS, then that has your oscillator and pwm in it.
you might try rubbing alcohol, you apply it and let it sit until it evaporates. the numbers might show up. if not rub some chalk on it. If you got that much of a number, then the number is probably laser etched into the chip. without it, you need like 5-10x magnification to read them a lot of times.
Isn’t it ironic, that after my soliloque on the virtue of AC motors – what do we see?
A bushed DC motor! AKA Universal Motor that contains a brushed-commutator-ring which connects stator windings to windings in the rotor via brushes. In other words: no permanent magnets and the rotor coil is switched by the commutator allowing the motor to operate with AC or DC power.
Next Pic: Top of the motor, commutator and brushes in AC-powered action connected to digital multimeter.
As you can see, the multimeter is ~16V below 124V line voltage caused by the stator windings.
Regarding the 12V inverter: Shout out to Sean O’Malley
I adjusted the screw top variable resistor and used the digital multimeter to monitor the AC output. Voltage decreasaed from 120 as the frequency increased from 60. The particular multimeter maxing out at 100hz and 98V. I was also able to measure voltage on the AC side of the transformer at 245V, but the frequency would not show on my device. I’m looking for an oscilloscope. Meanwhile, I’ve decided to offer the digital multimeter as pictured for sale. It comes with alligator clips.
Thank you for your consideration, and have a nice day.
Power moves from right to left:
Rotary Transformer - lowers mains voltage, according to dial: 0-120V
AC Multimeter - previously shown
Bridge Rectifier - Uses diodes and capacitor to convert AC to DC
DC Multimeter - This device measures DC voltage and current across a shunt
The DC multimeter was limited to 100V, and the readings were not consistent.
I was able to determine: The saw runs with less power during DC operation.
Run1
AC
42V
126W
3.6A
DC
70V
409W
5.8A
Run2
AC
60V
223W
4.5A
DC
97V
194W
2A
Thats as far as I could go because the DC multimeter stops at 100. BTW, it is also for sale please see my thread in the For Sale section. My guess is the shunt is not accurate for current near the 100V threshold because the DC meter showed the power going down as the voltage increased to that limit. And, the AC Multimeter is not supposed to go below 60V. It seemed to show impossibly low power consumption below 60V. Thus, these measurements were read out-of-spec: AC data from Run 1 and DC data from Run 2.
The old inverter was 400W and would not spin the saw at all. My new inverter has a different method of switching AC, which we will look at. The next two pics are both sides of a component of my new 1500W 12V car-battery inverter. I believe it’s what they call the PWM aka Oscillator, it generates the signal that goes to the MOSFETS. This is the same function that was done by the 555 time in my old inverter.
First, a big thanks for all who chimed in with info and corrections. In the past, I was thinking of the 555 timer as a microcontroller, but it’s known as an Integrated Circuit (IC) whose function is controlled with resistors and capacitors attached to the legs. An IC is basically a circuit board so small it fits in a chip. In the case of the 555 timer a resistor is used to slowly (in relative terms) fill a capacitor. Once that capacitor is filled to it’s threshold energy in the capacitor is emptied to the switch and the cycle repeats, up to a hundred times a second or more.
I know the 60hz signal is coming from that wide pin on the right in bottom pic.
I am trying to understand this board: where is the quartz crystal? Is that ugly thing the photocoupler? Can I replace this component with something that will let me change AC frequency during operation?
Thank you again for your consideration, input, and have a nice day.
You described oscillation without the use of a crystal. Because it is low-frequency, and ac can be a bit sloppy especially from low-end inverters.
PWM is a description of the signal itself. The signal is digital, it is either on or off. The on times vary in length of time they are on. If you look at it with a scope, the width of the peak gets wider but volts remain the same so the peaks are still all the same height, and look square or simply called square waves. It is similar to flipping on and off a light switch really fast. The avg light decreases for a dimming effect but the voltage remains the same.
I think what you found out is you don’t need a microcontroller to generate a pwm signal, and you don’t need crystal oscillator either.
If the big ugly thing is referring to the 16 pin IC. it is not a photocoupler. However that is the component you need to look up. The Ka3525a, which was also 16 pins, did seemingly use something similar to a 555 where the frequency could be controlled with external components. It could very well be a 555 baked onto the Ka3525a chip itself. But the spec sheet should tell you what pins and such.
I opened up another 12V inverter, this one a marine model with an array of smaller transformers. If you look to the orange arrow you can see 50hz and 60hz written on the board.
