Spot welder Control Board : Demo Video / pulse width


 Small  youtube video of the replacement control board.


There's a tiny bug where the rotary encoder button sometimes stops working, apart from that it works  really fine.

It is safer than the original one thanks to the LEDs/behaviour of the unit :

  • The state by default is "Off" and the unit can be safely manipulated. When it  is armed , the green LED is On. You can switch between Off and Armed easily.
  • The red light is a good indicator of a blown mosfet. If the red LED is on without contact => mostfets are blown. Similarily if the LED does not get lit when contact is made there is an issue.


How do we simply do a pulse of the right duration  ?

We program the PWM to have a total period of 100 ms and set the duty ratio to the pulse duration.

5 ms becomes 5% duty ratio.

We then stop the PWM after 75 ms. Since we have 25 ms to stop it, so it's not an issue to gurarantee it will be stopped in time.

That enables us to have accurate, hardware driven pulse without having to program the timer manually, by just using the PWM API.

The thing to be careful of is to do the PWM setup with interrupt disabled so that it's not in "not fully initialized state" ifever an interrupt happens right during in the middle.

Comments

Post a Comment

Popular posts from this blog

Component tester with STM32 : Part 1 ADC, Resistor

Image
I was always  fascinated by the so call "transistor testers" that identify and report pin out, features of pretty much whatever you throw at it. They are based on Atmel 328p chip, the same as arduino nano. So why not do the same thing with a STM32/Bluepill ? The STM32 is faster, has a better ADC accuracy, more memory, can do float etc... and is not more expensive. Warning : I'm doing this for fun & to learn, it might contain error & plain misunderstanding So, i watched a couple of video on the general principle on how they work. This is not a "port" but a rewrite from ~ scratch. When something is weird, i check what the original one does for comparison. Measuring resistance So first thing first :  Resistance & Capacitance. These 2 will unlock the other ones. So how do we measure resistance ? What we do is a resistor divider with a know resistance value: Measure = Vcc*(RtoTest/(RtoTest+Rknown)) As far as the ADC goes, it means ADC=
Read more

Fixing the INA3221

Image
It 's not too complicated to change the board we have seen  previously . You 'll need to cut some tracks, i did it with a dremel and i'm not very handy, so you'll do better. Red =Cut tracks Blue = Add wire 1- You'll need to separate the bottom connector from the ground, cut the 3 connectors BOTH SIDES. 2- Remove the small red area below the middle resistor to isolate each channels from each other Last, connect right side of each connector to the now isolated pad. Mine looks like this after the operation (ugly i know): Be wary of the small track on the left connector that leads to the left side of channel3 resistor. I cut it while isolating the right pad. Now it works, we can go back to the charger.
Read more

INA3221, weird wiring

Image
Continuing my "smart" battery charger, i've finally received the INA3221 module. It is the purple one you can find on ebay for ~ 5 bucks I soldered a couple of pins to be able to connect it so that i could test it and something immediately caught my attention. It is supposed to be a high side current/voltage sensor, typically in a setup like that : So you can measure the voltage supplied to the load, and the current going through it. Now, let's have a look at the module, look at the top of the following pic, where the sense connectors are. CH3/GND/CH2/GND/CH1/GND ? Wait ? What ? Yes, all the IN- pins are connected to ground, so it is a bottom current only sensor. Additionally, the - side of the shunts are ALSO connected to the ground, no only the connectors. The actual layout is like that : That raises two problems :  The voltage is meaningless as we are only measuring Current x ShuntValue, not the supply volt
Read more