[SOLVED] Pic 16f876a Pure Sinewave inverter

[robert.guttormson]

Can someone point me to the sub block in the schematic that generates the Zero cross pulses ?

 

[Californiajoe]

LM393 is a dual comparator, output should be PWM and PWM' at pin 1 and 7, check this on scope

I already did, signal is PWM and PWM'

---------- Post added at 08:07 PM ---------- Previous post was at 07:24 PM ----------

Well, I just noticed that A/B and PWM were exchanged between each other. So in scheme RC1 is A/B and RC2 is PWM. I am not sure if this is becouse of diferent MCU or mistake is somewhere in the code.
Could someone check this two signal for 16f876a?

Regards

 

[daniello_85]

Hi CaliforniaJoe

I can't check with oscilloscope your software and your signal but the inverter doesn't work, I've modify the analog value with trimmer but my inverter doesn't work.

 

[Californiajoe]

You mean, you upload my hex into your MCU and your inverter doesn't work? I suppose, you have 16f876a?

Regards

 

[daniello_85]

Yes, I have 16f876a. When I supply the inverter with your software, it's happening:

1) Turn on green led for 1second, then turn off
2)Turn on red led for 1 second, then turn off
3)Red led and green led turn off always.

I'm trying modify the value of analog input with trimmer (RA1, RA2 y RA5) but the inverter doesn't work. I don't understand it, It's very strange.

Best regards

 

[Californiajoe]

No, it is not strange, your MCU works well (you can see status LEDs), but I think, you have to modify Stdby and also Curr_h should be modified.
Maybe also Volt signal should be modified. Please check voltage level on each signal.

Regards

 

[daniello_85]

Hi CaliforniaJoe!

The value are:
V_OUT= 2.5V
curr_h= 2.5V
curr_l=2.5V (or 4.3V)
volt=4.6V
stdby=3V

The inverter doesn't work. Tell me the exact values and I will put them with my trimmer.
Regards!!:grin:

 

[Californiajoe]

Ok, here we have fresh measured values for all iputs.

b/a=1,3V
Stdby=0,5V
Volt=2,9V
Curr_h/Curr_l=1V
V_BAT=1,6V
V_OUT=2,5V

Also check PWM (20kHz) and A/B (50Hz) on MCU pins.

Regards

 

[daniello_85]

It doesn't work:???:

I don't understand it. The value is the same how you tell me. Could you check your software? I will check my schematic.

Best regards!

 

[Californiajoe]

Don't worry, load your working hex back to MCU. Can you tell me which version of hex is working one for you, I would test it?

Regards

 

[daniello_85]

OK, this is the file. I also will check my program.
Regards!:grin:

 

[Californiajoe]

your code works without red LED blinking. I didn't change trimers position to get it work, so I think also my hex should work on your board.

Regards

 

[daniello_85]

Hi californiajoe!!

I tried your hex again, but it doesn't work. Could you send me again the program? You compile it again and send me. It's very strange.

I connected the transformer and the output signal is the photo attachment. The problem is the voltage: isn't 220V, but this problem happen because the voltage between A-B is 6.5V and my transformer is 8Vac to 220Vac. Do someone know my problem? The frecuency between A-B is the 20Khz. I solved it my problem with the second signal, the frecuency between A-B mustn't 50Hz, it must 20KHz. The transformer is toroidal. Look the picture.

Best regards

 

[Californiajoe]

Frequency is between 46 and 47Hz, also PWM is ~19,4kHz and scope diagram looks sinusoidal to me.
So, you should have ~180-:-200VAC on secondar side of the transformer?
Please measure +U when transformer is powered.
Also don't forget to check temperature of output transistors!

Forget about my hex, you have a good one. Keep working with it.

Regards

 

[jami007]

daniello an ordinary transformer dosn't work with high frequencies so it some how behave like a filter here, at output it will be a 50 hz waveform, some transformers produce noise but some high quality do not. also the inverter output is 6-8 volt and you can adjust it from output control from 170V to a max of 230V using 8-230V transformer.if the output is between 200 to 240V I think all appliances work normally, there is always a (+)(-)5% relaxation. also in frequency 1-2% is nearly perfect.

also perform short circuit and open circuit tests for your transformer, also measure its core losses

After all You've done a Good job, when you finish share your experience with others

*** Bless You

 

[daniello_85]

Ok, I understood you tell me jami007.

The voltage in primary side of the transformer is 6.5V (ac). The voltage in secundary side of the transformer is 158V (ac). My transformer is toroidal and 150VA. The frecuency in my inverter is the 47Hz.

How can I adjust my inverter to have 8 volt to the primary side of the transformer? I will comment my experience because I used other component and other power transformer.

Note: I connected the PIN GND of the TLP250 (U3 and U4) to GND to my inverter does work.

Best regards!!:grin:

 

[Californiajoe]

Nice, you forgot to measure +U with powered transformer.
Very important for all of us:

Note: I connected the PIN GND of the TLP250 (U3 and U4) to GND to my inverter does work.

Keep good work!

Regards

 

[jami007]

RT1 is for output voltage adjust in the schematic, varying it you can vary output, the problem is not with the inverter. because its output is between 6-8V. the problem is with transformer, if it is an 8-220V transformer its output at 6.5V must be 178.75 ideally, but practically it must be around 170-175V due to core losses, as I said earlier perform following tests for your transformer, short circuit open circuit and also measure its core losses, insure the DC input of the circuit between 12V to 14.5V, an iron core transformer may work better with this circiut I suppose. the output may vary due to the resistance of the MOSFETs but not significantly.

---------- Post added at 07:12 AM ---------- Previous post was at 07:10 AM ----------

also 47Hz is nearly perfect for sine wave inverters, practically best inverters produce 47 to 49 Hz fraquency at output, so its excellent here

---------- Post added at 07:21 AM ---------- Previous post was at 07:12 AM ----------

Rt=47K is an NTC resistor (temperature sensor) and the software monitors the temperature of the MOSFEts if it goes high it turns on the fan and if it keep increasing after a certain value it turns OFF the inverter for safety purposes, so I think its not the thing we need to worry about if software works fine....

 

[daniello_85]

Ok jami007!!!Thank you very much!:grin:
Californiajoe I've measured the input voltage (+U) and output voltage (the secundary side of the transformer) with powered transformer. This are the values:

+U => Output (Secundary side transformer)
---- ---------------------------------------
12V (dc) => 151.2V (ac)
12.4V (dc) => 158.0V (ac)
14V (dc) => 187.4V (ac)
15V (dc) => 205.7V (ac)
>15V (dc) => Inverter doesn't work


Voltage in the primary side of the transformer is increased if the input voltage (+U) also increase. I have a doubt. If you looked the previous photo, you can see peak between positive side of sine wave and negative side of sine wave. I'm be going check the software and PWM signal with oscilloscope.What do you think?

Sorry, but, Like I've got work the inverter, I want make a perfect sine wave. Thank you very much everybody! I will comment my notes, ok?

Best regards

 

[Californiajoe]

What type of transistors do you have, it seems that you are loosing power on them.
Do you have output filter connected?

Regards