28-06-2024, 07:23 PM
The real reasons that the uTracer needs a minimum of an isolated fixed external supply at lower voltage isn't the current or the inductions:
1: The effective DC or sinewave voltage is Sqrt ( Vs x Va)
where Vs is the recycled laptop PSU (18 to 20V, mine is 19.1)
A table (slightly messed up.
1st column is the effective DC (or sinewave AC) set in the GUI
2nd Column is the measured average voltage for different supplies, the 19.1 internal is 1st.
(The 11.8 is really 11.78, but fudged for table)
Realistically about 4V is minimum usable at 19V supply, thus about 5V is maximum supply for 1V effective.
Thus minimums are:
Top row is supply.
Assuming the floating FET switch for an external supply working.
You'd need a big choke for filtered PWM, but then you'd still be limited by PWM resolution, however 1.4V might then be a minimum.
So really to see effect of heater voltage variation you need an external supply just about 10% to 15% more than rated filament/heater. Getting it to work with a floating FET switch and an external adjustable bench PSU will be nice.
1: The effective DC or sinewave voltage is Sqrt ( Vs x Va)
where Vs is the recycled laptop PSU (18 to 20V, mine is 19.1)
A table (slightly messed up.
1st column is the effective DC (or sinewave AC) set in the GUI
2nd Column is the measured average voltage for different supplies, the 19.1 internal is 1st.
Code:
PWM supply without a filter
Vsup 19.1 3.0 5.0 12 30 60 120
Veff Vav Vav Vav Vav Vav Vav Vav
0.7 0.03 0.16 0.10 0.04 0.02 0.01 0.00
1.4 0.10 0.65 0.39 0.16 0.07 0.03 0.02
2.1 0.23 1.47 0.88 0.37 0.15 0.07 0.04
4.0 0.84 3.00 3.20 1.33 0.53 0.27 0.13
5.0 1.31 3.00 5.00 2.08 0.83 0.42 0.21
6.3 2.08 3.00 5.00 3.31 1.32 0.66 0.33
12.6 8.31 3.00 5.00 12.0 5.29 2.65 1.32
15 11.8 3.00 5.00 12.0 7.50 3.75 1.88(The 11.8 is really 11.78, but fudged for table)
Realistically about 4V is minimum usable at 19V supply, thus about 5V is maximum supply for 1V effective.
Thus minimums are:
Code:
19.1 3.00 5 12 30 60 120
4.0 0.63 1.05 2.51 6.28 12.57 25.13Assuming the floating FET switch for an external supply working.
You'd need a big choke for filtered PWM, but then you'd still be limited by PWM resolution, however 1.4V might then be a minimum.
So really to see effect of heater voltage variation you need an external supply just about 10% to 15% more than rated filament/heater. Getting it to work with a floating FET switch and an external adjustable bench PSU will be nice.
