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Forum Index : Electronics : Bryan's Inverter build
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| tinyt Guru  Joined: 12/11/2017 Location: United StatesPosts: 516 |
Put back resistor bank and ribbon cable and repeat. Also measure voltage across the 120 ohms resistor. Edited 2026-03-07 15:06 by tinyt |
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Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1734 |
Ok the resistor bank voltage matched BV and settled 4 volts below the PSU voltage, now when the nano is turned the voltage quickly drops to 10 volts with a 200mA current draw. So turned it off |
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| tinyt Guru Joined: 12/11/2017 Location: United StatesPosts: 516 |
So looks like when the TIP41/TIP42's are driven by the nano, is when voltage (24-10 = 14) drops in the resistor bank, the way I understand it. The TIP41/TIP42's drive the mosfet gates which are high impedance unless some are leaking/shorted. I don't want to say this and I could be wrong, but looks like the power board needs some serious troubleshooting. |
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| Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1734 |
Just did some resistance measurements now with nano off the tip31 pins are 17 Vbat 17.7 volts now when the nano is turned on the voltage dropped to 10 volts 3.9 4.4 3.8 volts across the tip31 TIP42 on the right side of the board pin 1 (outside pin) to pin 2 (centre pin) 9.9K pin 1 (outside pin) to pin 3 ( inside pin) 11.8K pin 2 to pin 3 1.94K TIP41 pin 1 to pin 2 11.6K pin 1 to pin 3 11.8K pin 2 to pin 3 259K TIP42 on the left side of the board pin 1 to pin 2 9.9K pin 1 to pin 3 11.9K pin 2 to pin 3 1.9K TIP41 pin 1 to pin 2 650K pin 1 to pin 3 11.9K pin 2 to pin 3 350K |
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KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 2071 |
You have 60,000uF of capacitance across those FETS, you have at least a 2000 amperes discharge surge available from those caps. If you charge the power board, "And THEN enable the Nano controller", you will destroy things if those FETS switch hard on from a fault in the controller or power board. Apology if I misunderstand what you are writing, I won't mention this again! NANO:Inverter V 8.2ks - Linux AvrDude GUI script V3.3 |
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| mab1 Senior Member  Joined: 10/02/2015 Location: United KingdomPosts: 272 |
That's a very good point: at Vbat= 24v and R64=120ohms you're going to have less than 50mA drive current for all four totem pole drivers. 18 or 22ohms might be better for R64. R54 (r54 on the schematic, but looks like r64 on tinyt's pcb drawing) should be lower too: maybe 1k instead of 10K to provide enough base current for tip35. But i'm thinking it may be better if the powerboard was returned to the test bench, for better access for testing; once it's outputting 13v ac between vs1 and vs2 on the bench, it may be ready to go back in the cabinet with the big torroid. Edit again: Even if the above resistors are part if the problem, there has to be another issue causing the excessive current draw. Edited 2026-03-07 20:59 by mab1 |
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| tinyt Guru Joined: 12/11/2017 Location: United StatesPosts: 516 |
I think that 120 ohms 5 watts is there for a 48 volts battery to spread the heat between it and the TIP31/TIP35 used as a linear regulator. Here is an idea, only for your 24 volts psu with bank resistor testing: Temporarily jumper with a wire across the 120 ohms 5 watts resistor and re-do your testing. Edit: You might also need to change r64 from 10k to 1k per mab1's suggestion. Edited 2026-03-07 21:33 by tinyt |
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