I finally had some time to continue with this project. I built 4 complete units, 2 with +-54V and 2 with +-78V.
I tested first the 54V version (for UCD400OEM) without UCD connected. I I modified the resistor values to match 4-5V DC sensing for Picaxe according to post #140
* +-12Vdc on buffer rails as supposed
* +-55V main rail voltage on V+ and V- (see the schematic) as supposed
* +48V on H4/J4/VCC ALL THE TIME ???
* -55V voltage on H5/J5/VEE ALL THE TIME ???
When I first power up, the led flashes slowly for a while, then it starts to blink quickly.
I'm wondering why the positive rail voltage drops from 55V to 48V after the FETs. I'll have to triple check the wiring and I will test with the other units. Should it be so that if there is an error (led blinks fast) then voltage should not pass the FETs?
BR, Sami
I tested first the 54V version (for UCD400OEM) without UCD connected. I I modified the resistor values to match 4-5V DC sensing for Picaxe according to post #140
* +-12Vdc on buffer rails as supposed
* +-55V main rail voltage on V+ and V- (see the schematic) as supposed
* +48V on H4/J4/VCC ALL THE TIME ???
* -55V voltage on H5/J5/VEE ALL THE TIME ???
When I first power up, the led flashes slowly for a while, then it starts to blink quickly.
I'm wondering why the positive rail voltage drops from 55V to 48V after the FETs. I'll have to triple check the wiring and I will test with the other units. Should it be so that if there is an error (led blinks fast) then voltage should not pass the FETs?
BR, Sami
Hi Sami ,
Seems like the Picaxe is doing what it is suppose to do , Voltage after Fet's when they should be off , so give alarm .
One pin voltage is not mentioned here , pin 6 , should be 0 Volts , Fet's off !
Could you test your PSU with a load , say 1k , 3Watt resistor on each rail ?
You could also bypass the Fet OK test by fooling pin 5 and 3 and connect those pins with a 4k7 resistor to GND ( pin5) and 5V(pin3)
Good luck !
Cheers ,
Rens
Hi, Rens,
I placed 1k 5W resistors on both rails and the result is still the same. And the voltage on pin 6 was 0 volts.
Then I tried with the second unit. The result was pretty much the same, except this time positive rail after the fets had 0 volts and negative rail had around -55V, but now I noticed that the voltage was slowly dropping. It took a couple of minutes to drop till -25 Volts. Now I shut it of and immediately turned back on. Now the led blinked slowly and the started light continuously. The voltage on both rails after the fet was the same than before the fet. Then I shut it off, waited for a while and then turned back on. Now the both rails after the fets had around +-55V and slowly dropping. Again waited until +-25V and turned off and then back on and everything seemed ok.
I was able to replicate the same on the first unit.
I wonder what is going on?
Oh, and while the rail voltage after the fets was dropping the voltage on PICAXE pins 3 and 5 was also dropping.
-Sami
Looks like the picaxe is working OK , something else is wrong here with either the FET's or the VOM . Did you use the pin swap adapter for the VOM ?
if you remove R19 and R22 the FetFail test will always pass and the program goes to the DC test . The led should light constantly and pin6 shoul be 5V .Now you can check the DC_err function if you short DC_err to ground . pin 6 should go Lo and LED blinks SOS .
Cheers ,
Rens
Actually, VDR transformer was not connected at all on my tests.
I'll do some more tests later today. I'm suspecting the FETs, those could be fake, you never know. I'll try with some other type.
Above is OK , pins 3 and 5 are input on the PIC and measure rail voltage to determine if FET's are open or closed .
Cheers ,
Rens
I changed the FETs to some IRFB38..... which I had on hand. Now it works much better, I think the originals were fakes 
I powered on and the led lights constantly after 10 sec. Then I simulated DC-error by shorting the DC-error wire to ground. Now the led instantly started to blink SOS.
The PICAXE is definitely working as it should!
However, there is still a major problem. After the DC error the positive rail voltage drops to 0V in 10sec, but the negative rail voltage starts to drop very slowly, around 2V per 1 minute. What could cause this? What could be wrong in the negative rail? If you check the schematic of the VOM on the negative rail, is it correct, I'm confused now. I swapped the pins 3 and 4 on both positive and negative rail when the schematic/board error was found a couple of pages ago.
I powered on and the led lights constantly after 10 sec. Then I simulated DC-error by shorting the DC-error wire to ground. Now the led instantly started to blink SOS.
The PICAXE is definitely working as it should!
However, there is still a major problem. After the DC error the positive rail voltage drops to 0V in 10sec, but the negative rail voltage starts to drop very slowly, around 2V per 1 minute. What could cause this? What could be wrong in the negative rail? If you check the schematic of the VOM on the negative rail, is it correct, I'm confused now. I swapped the pins 3 and 4 on both positive and negative rail when the schematic/board error was found a couple of pages ago.
I changed the FETs to some IRFB38..... which I had on hand. Now it works much better, I think the originals were fakes
I powered on and the led lights constantly after 10 sec. Then I simulated DC-error by shorting the DC-error wire to ground. Now the led instantly started to blink SOS.
The PICAXE is definitely working as it should!
However, there is still a major problem. After the DC error the positive rail voltage drops to 0V in 10sec, but the negative rail voltage starts to drop very slowly, around 2V per 1 minute. What could cause this? What could be wrong in the negative rail? If you check the schematic of the VOM on the negative rail, is it correct, I'm confused now. I swapped the pins 3 and 4 on both positive and negative rail when the schematic/board error was found a couple of pages ago.
Hope you didn't fry your VOM's .
To check , remove FET's and measure output voltage on pin 3 and 4 of the MOV's . should be around 8V when FET's suppose to be open and drop to zero V instantly when FET's suppose to close .
The negative side schematic looks ok to me .
Cheers ,
Rens
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I'll try this probably tomorrow. Instead, I tried so that I just cut the wires leading from the VOM pins 3&4 on both rails. Now they don't connect to anywhere. This was the fastest way because of the "adapter".
Now led is not lighting at all and 0V on pins 3&4. And no voltage after the FET's. Then I accidentally shorted the pin 3 for a split second to where it was before cutting the wires. Now the voltage was the same after and before the FET's on negative rail. I had to put a discharge resistor on the rail (in test setup I have 33000uF per rail).
Doesn't this mean that the FET's won't close once they have been opened. Probable I should just remove the FET's and do the test properly?
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