"What I do is put a little solder on one of the pads on the pcb first. Then I pick up the resistor with a pair of tweezers (in the past I used fine nosed pliers but I find tweezers much easier to use) and place it on the pcb. At this point I use the iron to warm up the pad/resistor which melts the solder and forms the connection to one end of the resistor whilst also now holding it in place on the board. Then I take the iron to the other end of the resistor and with a tiny bit of solder finish the other joint."
Yes, that's the correct technique!
To do SMD you must have fine nose tweezers and a fine tipped soldering iron.
However, if you have eyesight and/or fine motor skills challenges, then I would agree that you should stick with THP.
Yes, that's the correct technique!
To do SMD you must have fine nose tweezers and a fine tipped soldering iron.
However, if you have eyesight and/or fine motor skills challenges, then I would agree that you should stick with THP.
Plus enough eyesight and dexterity
, which I have lost.You got it! That's my problem, so I have no choice if I want to continue hobbying. I love electronics and I missed it for years when I was not doing much with it. Now I am getting back into it more than ever, although quite impaired.
btw: I want to use your technique of SSRs for the rails. Those are simpler because it's just DC, but what would you recommend?
I need to be able to find the parts, I some seem harder to get where I am at the moment. Plus they must be through holes
There are a few places that make through-hole breakout boards for SMD parts. It's not reasonable for resistors, but you can obtain some common SOIC, SSOP and TQFP parts on little breakouts. Of course, obtaining the specific part that you want can be an issue because getting someone to custom-load a breakout board is expensive.
For example, breakouts at sparkfun.
For example, breakouts at sparkfun.
So, i'm close to pulling the trigger on the photovoltaic driver. Unfortunately, the only one i could find without buying from china via Ebay(and thus waiting a long time) is the TLP590B, which looks similar to a TLP191B, save for lacking an internal shunt resistor.
What do you think guys, will it work driving a pair of Fairchild FDH047AN08 TrenchFETs as long as i add an external shunt resistor?
The plan is to use 2 each as speaker output relays(for DC protection and to eliminate thump), according to Michael Bean's schematic earlier in the thread, and a single FET bypassing a fixed power resistor sitting between my SMPS and amp boards(to limit inrush current).
What do you think guys, will it work driving a pair of Fairchild FDH047AN08 TrenchFETs as long as i add an external shunt resistor?
The plan is to use 2 each as speaker output relays(for DC protection and to eliminate thump), according to Michael Bean's schematic earlier in the thread, and a single FET bypassing a fixed power resistor sitting between my SMPS and amp boards(to limit inrush current).
Thanks Jan, unfortunately i'm stuck with what's available at elfa.se. Also, it seems the Vishay VO3120 is an optocoupler and not a photovoltaic driver, and thus requires its own supply. Doesn't this also mean that for stereo use we will need two separate supplies? If not, how does one deal with the scenario of only one channel playing and a fault occuring?
I do have a separate supply but considering i need two speaker output relays and two current-limiting series resistors bypass relays, it seemed easier to wrap my brain around the scenario when using photovoltaic couplers/drivers.
I'll go back and re-read your clever solution which i have no doubt works earlier in the thread.
I do have a separate supply but considering i need two speaker output relays and two current-limiting series resistors bypass relays, it seemed easier to wrap my brain around the scenario when using photovoltaic couplers/drivers.
I'll go back and re-read your clever solution which i have no doubt works earlier in the thread.
The DC protect in my system came more as an added bonus, my amp is the Fetzilla, using integrated rail fuses, my main gripe was/is with getting rid of speaker thump at power-on(caused by off-spec K170s it turned out). And you're right, i don't need particularly fast switching behaviour. Bean used double photovoltaic arrays in his designs, to ensure full turn-on, it remains to be seen if just one array will do the trick in my design.
I'll go ahead and order the TLP590B's and start the experimentation.
The TrenchFETs i ended up getting are pretty beefy devices, and as such have a highish input capacitance(Ciss), of 6600pf. A pair means a grand total of 13.2nF of input capacitance for the chip to push in the case of the output relays. To the more math-savvy among us, what kind of switching times am i looking at?
I'll go ahead and order the TLP590B's and start the experimentation.
The TrenchFETs i ended up getting are pretty beefy devices, and as such have a highish input capacitance(Ciss), of 6600pf. A pair means a grand total of 13.2nF of input capacitance for the chip to push in the case of the output relays. To the more math-savvy among us, what kind of switching times am i looking at?
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If you assume the photo voltaic coupler output is a constant current source when fully turned on (quite a reasonable assumption), then from it=CV we get (13.2nF x 6V)/10 uA = 7.92 milliseconds.
The quoted Vgsth for this MOSFET is 6 V for 37 Amps Id, so it's a logic level device. In reality, you will have turned the load on or off more quickly than the 7.92 ms. Secondly, I assumed a photovoltaic output current of 10 uA.
The thing that's important is that the MOSFET remains within its SOA during the switching transition. But, I think it's good.
The quoted Vgsth for this MOSFET is 6 V for 37 Amps Id, so it's a logic level device. In reality, you will have turned the load on or off more quickly than the 7.92 ms. Secondly, I assumed a photovoltaic output current of 10 uA.
The thing that's important is that the MOSFET remains within its SOA during the switching transition. But, I think it's good.
Hi All, I did not read through the whole thread (sorry ), but did you consider protection solution, implemented within is a powerful regulated PSU (as soon as DC offset or current overload triggers, it immediately removes the power from the rails, saving the speakers and minimizing the damage for the rest of the amp). Of course, the big fat rail caps must be placed before the regulator, so that they don't slow down the power-off.
We discussed it with Damir (dadod) the other day (he showed me the practical implementation variant), I consider it as a good solution.
What's your view on this?
), but did you consider protection solution, implemented within is a powerful regulated PSU (as soon as DC offset or current overload triggers, it immediately removes the power from the rails, saving the speakers and minimizing the damage for the rest of the amp). Of course, the big fat rail caps must be placed before the regulator, so that they don't slow down the power-off.We discussed it with Damir (dadod) the other day (he showed me the practical implementation variant), I consider it as a good solution.
What's your view on this?
It doesn't prevent us from using a soft start with the relay, connecting the speakers in a couple of seconds, though some people don't like having the relay contacts between the amp and the speaker. In case of trouble, PSU cuts-off the rails and protection circuit follows with switching off the output relay, which will disconnect the speakers easily as no high current will be there already.
My overall idea is to operate the soft-start and protection in a normal way, but "kill" the rails quicker than the speaker relay switches off, letting it doing it nicely, in case of trouble (which is relatively easy to achieve).
I recommended this about 2 years back, I even discussed the turn on issue, looks to be easily solved with no relays.
You can search the thread, but there was not much response.
Obviously I am in accord with you and Damir, seems an excellent solution
Protects the amp too, and not just the speaker, eliminates primitive fuses, and eliminates even the idea of distortion from the protection FET/relay.
The fact that you don't have to endlessly repeat the case that the distortion is inaudibly tiny, is a major improvement just by itself.
It seems to have no downside at all, so I am not sure why it hasn't been more used.
Best wishes
David
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I recommended this about 2 years back, I even discussed the turn on issue, looks to be easily solved with no relays.
You can search the thread, but there was not much response.
Obviously I am in accord with you and Damir, seems an excellent solution
Protects the amp too, and not just the speaker, eliminates primitive fuses, and eliminates even the idea of distortion from the protection FET/relay.
The fact that you don't have to endlessly repeat the case that the distortion is inaudibly tiny, is a major improvement just by itself.
It seems to have no downside at all, so I am not sure why it hasn't been more used.
Best wishes
David
Hi David ,
Your recommendations 2 years ago are being discussed right now in this thread http://www.diyaudio.com/forums/class-d/255870-hypex-linear-psu-dc-error-protection.html, please read it and if you have any constructive comment please let us know .
Cheers ,
Rens
My PS regulator with all protection you can see here http://www.diyaudio.com/forums/powe...ply-cap-multiplier-electronic-protection.html and here http://www.diyaudio.com/forums/solid-state/182554-thermaltrak-tmc-amp-22.html#post3907062.
It was proven in real life.
Damir
It was proven in real life.
Damir