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Automatic line level detection

Update.
All paid for and delivered.

With one exception,
Thommy has paid but I have not posted out, pending his instruction to do so. He is in Cambodia.
 
My boards and relays arrived ages ago and are now in a drawer somewhere waiting for me to pull my finger out. I think because I changed my order half way from six to four units that I got four relays but six boards. I'll have a look and pm you - you could just pay Tony for the boards and I'll post them to you.
 
Can one of you just confirm that the BOM is still good to go please? I'm about to order 6x sets of components.
 
Just wondering, if by chance, there are any more pcbs available. Looking for anywhere from 2 - 6. Thanks.
 
I can order some if you like
quantity is multiplers of five.

Sorry for missing the post, I don't do much diy in summer.
 
Know what you mean. I keep hearing the pub calling. About the pcbs that would be great but before you do, any idea of how much it is likely to be? Cheers
 
Provisionally the boards around £2.00 each, Finder relay I get at 50% discount around £1.40 each plus postage and say a fiver for A pfm donation.
Boards take in the order of one month when I order them from China.
Regards
Tony
 
That's brilliant. I'll have 5 pcbs then and 4 "Finder" relays. If it's Ok with you perhaps you can PM me and I'll paypal you the funds by return. Thanks
 
Not sure of the exact costs but looking at the last orders I had

01/03/2015 PCB Qty. - 5 $15.90

04/08/2015 PCB Qty. - 10 $18.90

There is a little currency conversion charge and postage to yourself to be added.

Email me
tony at eclfirst dot co dot uk
 
Boards were same cost
10 boards are £16.58 GBP with shipping from China to me with currency conversion
Regards
Tony
 
The 6 volt regulator L78L06ACZ is now obsolete.
L78L06ABZ looks like a nice replacement RS 686-9439
The replacement has a MOQ of 25, if its a problem most any T092 package 6V positive regulator should do, its not a critical component, just needing to fit the board with the correct pin out and delivering a 6 volt biasing reference.

Latest version

SCHEMO_zps483773a2.png


Current BOM

Terminal block 2 way PCB TE Connectivity 282841-2 - RS 710-0362
(Better, more robust terminals are the four gang RS 710-0374)
Board headers 2.54mm pitch turned pin or similar.
TR1 – Transformer PCB 1.8VA 2x9V Myrra 44128 RS 173-9721
D1, D2, D3, D4 – diode Vishay 1N4001-E3/73
Q1 – 2N7000
A1, A2 – TL061CN - RS 355-5042
VR1 – TO92 voltage regulator,L78L12ACZ 12V RS 189-1302
VR2 – TO92 voltage regulator,L78L06ABZ 6V RS 686-9439
C1 – Electrolytic 470uF 25V 5mm pitch 10mm diameter – Lucky bag
C2, C3, C4, C5, C6, C7 – Kemet C320C104K5R5TA Radial X7R ceramic cap,100nF 50V 2.5mm pitch - RS 538-1310
C8 – Electrolytic 100uF 25V 2.5mm pitch 7mm diameter – Lucky bag
R1, R2 – Resistor metal film 1% ¼ W 10K
R3, R4, R5, R7 – Resistor metal film 1% ¼ W 100K
R6 – bourns 3296Y-1-203LF top adj cermet trimmer,20K 10mm RS 522-0142
R8, R9 – Resistor metal film 1% ¼ W 100R
R10 – Resistor metal film ¼ W 10M
R11, R12 – Resistor metal film 1% ¼ W 4K7 Adjust to suit LED
K1 – Finder 40.52.7.012.0000
K2 – Relay DPDT PCB sub-minature,1A 12Vdc omron G6K2P12DC RS 683-9683


Bottom copper
BOT_zps44242c7e.png


Top copper
TOP_zps52d78df4.png


Components
COMP_zps0afda71a.png
 
How does the force on function work, is it a momentary connection that brings the timer circuit to life?

Also what is the S/B pad for?
 
thommy said:
How does the force on function work, is it a momentary connection that brings the timer circuit to life?

Also what is the S/B pad for?
Click to expand...

Force operation X5-1 & X5-2 if made will force the main relay on.
If released will return the circuit back to normal automatic operation.
The link just applies power to the main relay coil. Actually a return path as the relays have a permanent 12v0 on the A1 terminals. Or if you like a manual on command.


Force standby operation X4-1 & X4-2 if made will force the main relay off.
If released will return the circuit back to normal automatic operation.
The link discharges the timing capacitor C8.

X4-2 is also a useful point to monitor the relay drive status when setting the sensitivity potentiometer.
From memory you find the relay picks up around 1v7. As signal is detected this voltage rises from around 0v0 to close to rail at 12v0. The voltage slowly decays over around 15 minutes in absence of signal detection due to time constant set by R10 and C8. Linking X4-1 & X4-2 forces the voltage on C8 to decay rapidly saving you to wait around whilst setting the potentiometer. Or if you like a manual off command.

Again from memory, turning the potentiometer clock wise increases the signal detection threshold.
Not high enough threshold and the system will either not power on or drop out during quite passages. Too higher a threshold and it would never drop out.

Play some music and adjust the potentiometer clockwise until the system powers on, it only takes a short moment to power on.
Monitor the voltage at X4-2 and stop playing music, you will see the voltage slowly fall over fifteen minutes or so. The relay drops off around 1v7. Turn the potentiometer anti clockwise a little if the voltage stays high.

Roughly how it works...
So signal comes in, gets decoupled and floated to around half rail at 6v0.
The first amplifier applies a lot of gain to the signal to get something half decent to work with.

The second amplifier compares the previously amplified signal with a reference voltage set by the potentiometer (about half rail voltage) and pops out a short swing to the high rail on its output when the comparison is true. (It works on only one half of the incoming signal waveform)
The short pulses from this amplifier then charge relatively slowly (say a secound) the capacitor C8 and hence the gate of the 2N700 FET Q1. This is a nifty little general purpose driver that is happy without any support components and drives the relay coils.
The second little Omron relay is only used to drive the status LEDs.
Way back PD suggested the TL061CN as it has a very low quiescent power.
Originally I used a pair of resistors to derive the half rail voltage but found it needed a rather stiff divider network and consumed a noticeable amount of quiescent power, the 6v0 regulator was added to negate this negative aspect.

Hope this is clear to understand.
It will all become much clearer when you build the circuit have a measure on X4-2 and twiddle the potentiometer.

There are now around fifty of these boards out in the wild and no one had any problems with setup.

Regards
Tony
 
Could it be used to power up a dac with a single press of a button and leave it powered on long enough to start some music playing? Or will it go off again when i release the button.
 
It could, the button press charges the cap which keeps the circuit on until the level dictated by the setting Tony describerd above. Just leaving it in auto position is probably best
 
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