LM1875 exhibits large turn "ON" & "OFF" thump regardless of whether you use SPDT or DPDT as a power switch. I've crudely measured the DC to be > 2.5V.
Soln.
1 Use DPDT to turn spk. connections "ON" & "OFF" (once your chipamp stabilises). If you are using single supply then put 200R/ 1W from o/p capacitor to GND proceeded by DPDT switch.
2 Use soft start / DC protection boards employing relays.
Soln.
1 Use DPDT to turn spk. connections "ON" & "OFF" (once your chipamp stabilises). If you are using single supply then put 200R/ 1W from o/p capacitor to GND proceeded by DPDT switch.
2 Use soft start / DC protection boards employing relays.
It is "safer" to use a double pole switch.
Electrically 1pole is identical to 2pole.
That is NOT the reason for pop/thump/crack/click/etc.
If you add speaker delay relay with instant OFF, it will prevent start up and shut down surges from reaching the speaker.
It won't stop clicks/cracks which are at the instant of opening the switch.
Electrically 1pole is identical to 2pole.
That is NOT the reason for pop/thump/crack/click/etc.
If you add speaker delay relay with instant OFF, it will prevent start up and shut down surges from reaching the speaker.
It won't stop clicks/cracks which are at the instant of opening the switch.
The ARRL advises US ham radio ops to use SPST for 117 lines. If you have a 1kW amplifier running off 220 then you would use DPST.
Practice varies -- a lot of test equipment which would be used in the US or Europe (where the trafo might be rewired) may have a DPST switch.
You can use a Mallory "Quench-Arc" across the switch. The contacts of the switch are like the plates of a capacitor and as they get close a spark may jump across the contacts.
Practice varies -- a lot of test equipment which would be used in the US or Europe (where the trafo might be rewired) may have a DPST switch.
You can use a Mallory "Quench-Arc" across the switch. The contacts of the switch are like the plates of a capacitor and as they get close a spark may jump across the contacts.
AndrewT lives in the UK, correct.
The UK does not use a balanced dual Live and Neutral.
The UK uses a single Live and a single Neutral in most domestic premises. I happen to have 3phase (400Vac) but that is unusual for domestic.
The alternative is 3phase, which is generally available in commercial/industrial premises.
But for domestic: the UK requires 2pole switching for plug/socket outlets. Lighting with fixed wiring can use 1pole switching.
In countries that use non polar (reversible) plug tops: there the Live and Neutral can be swapped. It is very important that 2pole switching is used.
In countries where polar (that can't be reversed) plug tops: the Live and Neutral can be miswired (as they can be in the UK) and switching of only 1pole can leave equipment LIVE even though switched off.
2pole switching is safer in all countries, irrespective of what plug/socket type is used.
The UK does not use a balanced dual Live and Neutral.
The UK uses a single Live and a single Neutral in most domestic premises. I happen to have 3phase (400Vac) but that is unusual for domestic.
The alternative is 3phase, which is generally available in commercial/industrial premises.
But for domestic: the UK requires 2pole switching for plug/socket outlets. Lighting with fixed wiring can use 1pole switching.
In countries that use non polar (reversible) plug tops: there the Live and Neutral can be swapped. It is very important that 2pole switching is used.
In countries where polar (that can't be reversed) plug tops: the Live and Neutral can be miswired (as they can be in the UK) and switching of only 1pole can leave equipment LIVE even though switched off.
2pole switching is safer in all countries, irrespective of what plug/socket type is used.
Last edited:
Switch-off pops can usually be cured by putting an X cap (maybe 10nF) across the mains transformer primary - after the switch.
SP or DP switch makes no difference to pops, but big difference to safety. Only use SP if you can absolutely guarantee no wiring faults will ever occur anywhere within your building or between that and the power company transformer.
SP or DP switch makes no difference to pops, but big difference to safety. Only use SP if you can absolutely guarantee no wiring faults will ever occur anywhere within your building or between that and the power company transformer.
This is very wise advice, even if you don't have higher voltage like the UK. (220 will do more than just knock you on your rear. As all the British engineers I've worked with have said, it'll clean your clock and put you in a hole in the ground.)
I have seen terrible household and industrial miswiring, and it is not uncommon to see hot and neutral reversed, as it is something I always check. Sometimes the physical wiring so bad that I wonder if electricians are often drunk in addition to being simply incompetent and ignorant of the code.
Always best to completely isolate equipment with a DT switch or relay. Your local hardware store will sell you a tester for the price of lunch that lights up for proper wiring, hot reversed, neutral reversed, and bad ground.
I also replace standard outlets with GFIs for similar reasons. Saved some people from shocks a few times when equipment had internal short. More than once someone complained that the GFI kept tripping so it must be defective (not the load) and they wanted the GFI outlet replaced with a regular one to solve the problem as "this doesn't happen anywhere else".
I once opened up a work light that kept tripping the GFI and discovered that the stranded wiring wasn't properly twisted, and as a result a few strands were in contact with the housing so it was live. I pointed to the problem and said, next time a GFI saves your life don't blame it for malfunctioning.
Absolutely right. I am aware of two electricians that were killed because they thought they had switched off a circuit. A DPDT switch can short on the hot side and give the indication of being off when the circuit is still dangerous.
My understanding is that this refers to breakers or fuses for the main house wiring, not for appliances, and, indeed, the code prohibits this.
Generator transfer panels must switch both hot and neutral, for obvious reasons.
I have seen numbers ranging from 0.5-2% for miswired home electrical circuits in the US. My personal experience—based upon the small sample size of every apartment I've lived or those for my friends—is that at least one miswired outlet is always present. My current apartment had 2 out of 11 outlets miswired, about 20%.
BUT, then again, my friends and I live in old buildings with antediluvian electrical systems because we're not rich, so YMMV. I'm sure newer buildings are wired better. Although when my parents had their kitchen renovated the electrical inspector did NOT check the wiring. It was all perfect, but that's not the point; the inspector simply did not check.
My Lounge has 8 double socket outlet plus 3 socket outlets for table lamps. Even the kitchen has 6 double socket outlets.
The whole 4bedroom house (~200m²) has ~90 power sockets.
All have been checked during construction and rechecked by me using that simple and cheap plug in tester.
0% miswired.
And I still use double pole mains switching in my equipment, when switching is included. Some have an IEC inlet socket in lieu of a mains switch.
Last edited:
Anything pre-Tropical Storm Sandy is, by definition "antediluvian" -- at least south of 23rd St.
Now... As a fan of Edison I'm using nothing but 12v/24v DC, so what is the story there?
The neutral of my battery bank is earthed so I could safely use SPST throughout however in the event of high voltage coming into contact with either my solar panel system/loads/battery bank I would need to leave Negative connected so the case of my projects don't become live. Correct?
The solar panel is supposed to be earthed. as part of Australian design code.
The battery bank must be earthed on the negative. as part of code.
There must be a breaker on the solar panels and on the battery bank from the load.
And all wiring must be run through "heavy duty conduit", i'm assuming that means metal conduit.
And of course signs setup for emergency personell's safety.
I may have to run a third earth wire for all loads? That way it shouldn't matter if I use SPST and disconnect positive only or use DPDT and disconnect both positive and negative at the same time.
If all else fails take the safest route. DPDT throughout with a dedicated earth wire.
Please note, I'm talking about a low voltage 12/24v DC system here.
As for fusing, I'm thinking of just fusing the positive side as usual.
The neutral of my battery bank is earthed so I could safely use SPST throughout however in the event of high voltage coming into contact with either my solar panel system/loads/battery bank I would need to leave Negative connected so the case of my projects don't become live. Correct?
The solar panel is supposed to be earthed. as part of Australian design code.
The battery bank must be earthed on the negative. as part of code.
There must be a breaker on the solar panels and on the battery bank from the load.
And all wiring must be run through "heavy duty conduit", i'm assuming that means metal conduit.
And of course signs setup for emergency personell's safety.
I may have to run a third earth wire for all loads? That way it shouldn't matter if I use SPST and disconnect positive only or use DPDT and disconnect both positive and negative at the same time.
If all else fails take the safest route. DPDT throughout with a dedicated earth wire.
Please note, I'm talking about a low voltage 12/24v DC system here.
As for fusing, I'm thinking of just fusing the positive side as usual.
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.