I want to monitor the presence of voltage on each of the three phases in my house (230/415Vac). We suffer very frequent power cuts.
I can put in a diode followed by a resistor then a LED.
The resistor dissipates quite a lot of power. or
I could use a constant current source but it would need to be Hi Voltage. or
I could wire in three transformers & then LED at low volts.
I don't like any of my solutions.
Can anyone suggest a cheap, safe & simple circuit?
regards Andrew T.
I can put in a diode followed by a resistor then a LED.
The resistor dissipates quite a lot of power. or
I could use a constant current source but it would need to be Hi Voltage. or
I could wire in three transformers & then LED at low volts.
I don't like any of my solutions.
Can anyone suggest a cheap, safe & simple circuit?
regards Andrew T.
You can check my softstart and how I drive both a LED and relays.
As noted, beware of transient protection becasue they go just right through the cap.
http://home.swipnet.se/~w-50719/hifi/sst01
As noted, beware of transient protection becasue they go just right through the cap.
http://home.swipnet.se/~w-50719/hifi/sst01
Hi All,
Do I understand this correctly?
build a string of diode, cap, and LED. The diode only lets half the AC waveform through, the cap acts as a voltage reducer without power loss (no heating) and then the LED lights up.
Q1: Do I need a resistor in parallel with the cap as shown in Peranders schematic?
Q2: Do I need a resistor in series with the LED?
Thanks so far
Andrew T.
Do I understand this correctly?
build a string of diode, cap, and LED. The diode only lets half the AC waveform through, the cap acts as a voltage reducer without power loss (no heating) and then the LED lights up.
Q1: Do I need a resistor in parallel with the cap as shown in Peranders schematic?
Q2: Do I need a resistor in series with the LED?
Thanks so far
Andrew T.
Almost
Connect the cap is series with a LED and Diode That are parallel ,but opposite Anode to cathode and cathode to anode.
As the cap charges on the positive swing, it'll flow current through the led, as it discharges and charges neg, it'll flow current through the diode (preventing too much reverse voltage, damaging the led)
Connect the cap is series with a LED and Diode That are parallel ,but opposite Anode to cathode and cathode to anode.
As the cap charges on the positive swing, it'll flow current through the led, as it discharges and charges neg, it'll flow current through the diode (preventing too much reverse voltage, damaging the led)
Q1: It's common pratice to have a bleeder because it's quite unpleasant if you touch 100 nF or more charged with 300 V DC worst case.AndrewT said:
Q2: You should have a transient protection of 3.4-6.8 volts, Zener 1.3 watts or a tranzil.
(Cap//bleeder) + (Res 1-2 Watts) + (Zener//(Res+ LED))......(//= in parallel with)
The resistor may be 100 or something whoch will limit the LED current at zener voltage.
Cap = 100-470 nF(250 VAC/630 VDC) at 230 VAC
Bleeder = 3-5 X 100-470 kohms, 0.6W metall or high voltage types, like 1250 volts total resistance, 220k-1.5M ohms
Res 1-2 W = 470 ohms- 1k
Zener = 1.3 W, 3.4-6.8V, or tranzil 600W
Res(LED) = 100-220 ohms 0.25 W
LED = any kind
Let's get back to basics. The capacitor has the nice property of being a resistance (actually reactance) without generating heat, so is the main voltage dropper.
Reactance = 1/2.Pi.f.C, so a 0.33uF will be 9645R on our 50Hz. Add a 1k series resistor to limit surge as the capacitor first charges, led current will be 22mA RMS on 230V AC but only half the time, the resistor will produce 0.48W so no big problem, a 1W will do.
You still need a 1N4004 in inverse parallel with the led to protect it from reverse current.
Another thought would be to just run SPCO relays on the mains, with a battery-powered buzzer to act if the coil loses power.
Reactance = 1/2.Pi.f.C, so a 0.33uF will be 9645R on our 50Hz. Add a 1k series resistor to limit surge as the capacitor first charges, led current will be 22mA RMS on 230V AC but only half the time, the resistor will produce 0.48W so no big problem, a 1W will do.
You still need a 1N4004 in inverse parallel with the led to protect it from reverse current.
Another thought would be to just run SPCO relays on the mains, with a battery-powered buzzer to act if the coil loses power.
simple circuit...
remember those rechargeable torches without transformers.
They had .33µF/400VAC cap, and a 1M R in parallel. Next was a bridge made from signal diodes, and battery of two big NiCd button cells connected across + and - and the bridge returns back to mains with a 330 Ohm series resistor.
In this connection, long back, I happened to read that 1µF will give a charging current of 40mA.
From this, I had made a simple mains indicator
A 0.1µF cap 250Vac(x2 type) with 470K resiator in parallel, Two anti-parallel LEDs (A to K, K to A), and a series resistor of 470 ohms returns to mains.
the 470K R discharges the C
two LEDs in parallel as connected takes care of reverse voltages
the 470 ohms R acts as a protection(in case something fails)
all of the above was assembled in a three pin plug.
0.1 µF cap is just because I had one. U can put a bigger value. A little higher current will not affect the LEDs since it's AC half wave per LED.
There was an instance when all the three phase indicating Zero bulbs were lighting, and a three phase motor was not running. Gone to check and found out out that there were only two phases and the third was not wired.
So I suggest for foolproof indication, incase of 3 lines (not phases) wire the indicators across the lines. Values as per line voltage i.e. 415V.
Gajanan Phadte
remember those rechargeable torches without transformers.
They had .33µF/400VAC cap, and a 1M R in parallel. Next was a bridge made from signal diodes, and battery of two big NiCd button cells connected across + and - and the bridge returns back to mains with a 330 Ohm series resistor.
In this connection, long back, I happened to read that 1µF will give a charging current of 40mA.
From this, I had made a simple mains indicator
A 0.1µF cap 250Vac(x2 type) with 470K resiator in parallel, Two anti-parallel LEDs (A to K, K to A), and a series resistor of 470 ohms returns to mains.
the 470K R discharges the C
two LEDs in parallel as connected takes care of reverse voltages
the 470 ohms R acts as a protection(in case something fails)
all of the above was assembled in a three pin plug.
0.1 µF cap is just because I had one. U can put a bigger value. A little higher current will not affect the LEDs since it's AC half wave per LED.
There was an instance when all the three phase indicating Zero bulbs were lighting, and a three phase motor was not running. Gone to check and found out out that there were only two phases and the third was not wired.
So I suggest for foolproof indication, incase of 3 lines (not phases) wire the indicators across the lines. Values as per line voltage i.e. 415V.
Gajanan Phadte
Automatic changeover...not for beginners
Newbies DO NOT ATTMPT THIS.
Sometimes it becomes necessary to have auto phase changeover, especially for the bedroom for having the airconditioner, a fan or whatever running through whichever phase alive. U are not going to get up in the/after midnight and be satisfied looking at the 2 out of three monitor lights glowing.
For this u need two contactors with minimum 1 changeover contact on each.
Phase 1 - Ph(live) is wired to the coil and N/O contact of the same contactor(No.1)
Phase 2 - Ph(live) is wired to the coil and N/O contact of the same contactor(No.2)
Common contact on No.1 is shorted to N/C contact on No.2
Phase 3 Live/Ph is connected to N/C contact on No.1 and the output is taken from the Common contact of No.2.
The contactors SHOULD...
1. have proper mains voltage rating for the coil and contacts
2. have BREAK BEFORE MAKE contacts.
3. have contacts of sufficient current rating and should be overrated for motor starting currents.
If u do not know what happens to the neutral, DO NOT ATTEMPT THIS.
If u have the slightest doubt, U SHOULD NOT ASSEMBLE THIS.
ASSEMBLE AT YOUR OWN RISK
Reminder
Newbies DO NOT ATTEMPT.
Gajanan Phadte
Newbies DO NOT ATTMPT THIS.
Sometimes it becomes necessary to have auto phase changeover, especially for the bedroom for having the airconditioner, a fan or whatever running through whichever phase alive. U are not going to get up in the/after midnight and be satisfied looking at the 2 out of three monitor lights glowing.
For this u need two contactors with minimum 1 changeover contact on each.
Phase 1 - Ph(live) is wired to the coil and N/O contact of the same contactor(No.1)
Phase 2 - Ph(live) is wired to the coil and N/O contact of the same contactor(No.2)
Common contact on No.1 is shorted to N/C contact on No.2
Phase 3 Live/Ph is connected to N/C contact on No.1 and the output is taken from the Common contact of No.2.
The contactors SHOULD...
1. have proper mains voltage rating for the coil and contacts
2. have BREAK BEFORE MAKE contacts.
3. have contacts of sufficient current rating and should be overrated for motor starting currents.
If u do not know what happens to the neutral, DO NOT ATTEMPT THIS.
If u have the slightest doubt, U SHOULD NOT ASSEMBLE THIS.
ASSEMBLE AT YOUR OWN RISK
Reminder
Newbies DO NOT ATTEMPT.
Gajanan Phadte
Hi gmphadte,
Wow that reply has got me thinking about another project.
But I think it might be safer to leave it to a professional electrician.
I just want to know which parts of the house have lost power. Each time I report a fault the power co. do not believe me & ask me to test in case it is an internal fault. Last time they did not issue a work permit until after a second customer reported the fault some 9 hours after the failure.
regards Andrew T.
Wow that reply has got me thinking about another project.
But I think it might be safer to leave it to a professional electrician.
I just want to know which parts of the house have lost power. Each time I report a fault the power co. do not believe me & ask me to test in case it is an internal fault. Last time they did not issue a work permit until after a second customer reported the fault some 9 hours after the failure.
regards Andrew T.
I have drawn a schematic of the LED driver but as pointed out: Lethal voltage!!! 
I have made a pcb but I have no plans to manufacture any. I drew this schematic because this question pops up now and then. Notice that you can make it simplier but it will be more sensistive against transients and will brake easier.
Forget about the describing text, I have copied the whole section from an another project. I will add more describing text.
http://home.swipnet.se/~w-50719/hifi/mld01
I have made a pcb but I have no plans to manufacture any. I drew this schematic because this question pops up now and then. Notice that you can make it simplier but it will be more sensistive against transients and will brake easier.
Forget about the describing text, I have copied the whole section from an another project. I will add more describing text.
http://home.swipnet.se/~w-50719/hifi/mld01
Four important rules for connecting anything to the mains.
use a very well insulated enclosure. Plastic cases are fine if they are sufficiently IP rated. Ordinary cheap plastic boxes will not do.
make your connections as physically strong as possible (soldering won't do), twist and wrap everything first. Insulate every possible connection so that no possible contact can be made (by humans or the cat) with the wiring even if the box were exposed.
Ensure that you will never wire your other phases together even by accident.
A few words about the LED mounting....
If you're using a Chrome metal LED mount, a plastic enclosure will NOT do. You will have to then use a metal box, and provide an unmovable connection to earth for safety. If the LED fails, there is possibility that the metal holder could become live at mains, and you will not enjoy touching this whilst standing in your pyjamas on a stone floor at 2am.
Using a plastic mount invites the possibility of the LED being pushed inside the box, rendering any wiring exposed. Again ensure all connections are as short as possible, and well insulated.
I would never advocate that any novice builder should connect or make circuits that directly connect to mains potentials. I pray that you're lucky, have a change of heart, or use an isolation transformer/step-down or a better arrangement than the 'capacitance dropper' which is no better than DJ Sound to light TRIAC controllers - cheap, cheezy, and one touch is fatal!
Switch to safety, MAINS KILLS
use a very well insulated enclosure. Plastic cases are fine if they are sufficiently IP rated. Ordinary cheap plastic boxes will not do.
make your connections as physically strong as possible (soldering won't do), twist and wrap everything first. Insulate every possible connection so that no possible contact can be made (by humans or the cat) with the wiring even if the box were exposed.
Ensure that you will never wire your other phases together even by accident.
A few words about the LED mounting....
If you're using a Chrome metal LED mount, a plastic enclosure will NOT do. You will have to then use a metal box, and provide an unmovable connection to earth for safety. If the LED fails, there is possibility that the metal holder could become live at mains, and you will not enjoy touching this whilst standing in your pyjamas on a stone floor at 2am.
Using a plastic mount invites the possibility of the LED being pushed inside the box, rendering any wiring exposed. Again ensure all connections are as short as possible, and well insulated.
I would never advocate that any novice builder should connect or make circuits that directly connect to mains potentials. I pray that you're lucky, have a change of heart, or use an isolation transformer/step-down or a better arrangement than the 'capacitance dropper' which is no better than DJ Sound to light TRIAC controllers - cheap, cheezy, and one touch is fatal!
Switch to safety, MAINS KILLS
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