Gallery, Projects and General > Project Logs
Induction heater project
eskoilola:
--- Quote from: awemawson on May 21, 2018, 11:48:37 AM ---If you look at one of the photos of mine you will see that power is monitored by ....
--- End quote ---
It was Your pictures that made me rethink the current measurement. They are actually quite helpful ... cannot reverse engineer the schematics of that controller though :bang:
Here is a mockup of the user interface and some of my thoughts of the functionality.
Far left are the mains switch and the mains indicator light.
The three round knobs on the bottom are for adjusting the heat up, sustain and cool down times. The time range for each might be one hour.
The yellow buttons on top of the three knobs are buttons/lights. When a particular phase is running then a corresponding button has it's light turned on. It would be possible to enter any phase just by pushing corresponding button.
The big knob is the power. Range is from zero to 100%
On top there are three status lights/buttons.
Temperature/cooling status. When running OK the light stays on and when in error the light blinks.
Next status light/button is current/voltage measurement. The light is on during normal operation and will blink when in fault.
The last status light/button is a generic fault. When operating normally the light is tuerned on and in error this blinks
When the heating process is running pushing any other than the phase buttons will abort the process
When the heating process is not running then pushing the coolant button will start the coolant system and sets the light blinking. Pushing again will stop the coolant system.
awemawson:
--- Quote from: eskoilola on May 21, 2018, 12:19:55 PM ---
It was Your pictures that made me rethink the current measurement. They are actually quite helpful ... cannot reverse engineer the schematics of that controller though :bang:
--- End quote ---
Actually back in 2005/6 I did go a long way to working out that controller - I got it down to 'block' level and component level for some of it. I then managed to chat up a girl at CFEI who copied a manual for me - still got it somewhere, I'll dig it out and see how detailed it is - it was a long time ago and much water has flowed under the bridge since then :bugeye:
PekkaNF:
OT....maybe....
--- Quote from: eskoilola on May 21, 2018, 11:10:17 AM ---.... and the experiences I have from hall sensors are not that encouraging.
I made a hall sensor thing for one of my friends to measure the windmill output current and that sensor was far from accurate. The result depended on the orientation with earth magnetic field - this had to be compensated and in addition those ferrites have some sortr of a hysteresis so that after a decent current spike there was remaining magnetism which affected the result as well.
...
--- End quote ---
Do you mind opening up a new (short) thread for it? I'm interested how did you do it and how it went wrong. To my understanding shunt resistor/kelvin connection is most accurate (and problematic too), then current transfomer is prefered on mains frequency and HAL is used when those don't fit.
I have semidecent, pretty cheap Hal probe for oscillsocope and I suspect it uses the universal priciple of using HAL.to detect "zero" flux, ie. there is a compensation winding to generate opposite flux to flux generated by measured current:
https://meettechniek.info/instruments/scope-probes.html
https://www.digikey.com/en/articles/techzone/2017/aug/understanding-selecting-effectively-using-current-probes
This is something I haven't eperimented first hand..might be all BS.
Pekka
eskoilola:
--- Quote from: PekkaNF on May 21, 2018, 02:23:02 PM ---Do you mind opening up a new (short) thread for it? ...
--- End quote ---
The thread
Pete W.:
--- Quote from: PekkaNF on May 21, 2018, 02:23:02 PM ---OT....maybe....
--- Quote from: eskoilola on May 21, 2018, 11:10:17 AM ---.... and the experiences I have from hall sensors are not that encouraging.
I made a hall sensor thing for one of my friends to measure the windmill output current and that sensor was far from accurate. The result depended on the orientation with earth magnetic field - this had to be compensated and in addition those ferrites have some sortr of a hysteresis so that after a decent current spike there was remaining magnetism which affected the result as well.
...
--- End quote ---
Do you mind opening up a new (short) thread for it? I'm interested how did you do it and how it went wrong. To my understanding shunt resistor/kelvin connection is most accurate (and problematic too), then current transfomer is prefered on mains frequency and HAL is used when those don't fit.
I have semidecent, pretty cheap Hal probe for oscillsocope and I suspect it uses the universal priciple of using HAL.to detect "zero" flux, ie. there is a compensation winding to generate opposite flux to flux generated by measured current:
https://meettechniek.info/instruments/scope-probes.html
https://www.digikey.com/en/articles/techzone/2017/aug/understanding-selecting-effectively-using-current-probes
This is something I haven't eperimented first hand..might be all BS.
Pekka
--- End quote ---
There is another way that doesn't need the magnetic field sensor. You detect the second harmonic of the input signal generated by the magnetic non-linearity of the core material. Then you use that signal to servo the compensation current to drive the second harmonic to zero amplitude. Very similar to how a flux-gate magnetometer works.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version