Hi all,
To monitor the dual power rails for my HP amp , I made a simple under and over
voltage detector , which switches off the power (and relay) , and gives an indication of what went wrong.
It works as it should , BUT I noticed when doing tests that it gets triggered by starting a fluorescent tube lighting or touching inputs just with a test lead.
Grounding the inputs without the 47k resistors or connecting the inputs with other
HCmos outputs , no problem , but the problem is now also on the optocoupler's
transistor side. When the opto transistor is off , again triggered by fluorescent tube
lighting starter.
Will encasing it in an Aluminium casing solve this ?
Now I made lots of Cmos devices , never had this problem , but now I live in a
electrosmog environment , with lots of badly laid , overhead power wires and a
nearby WiFi transmitter. I had an computer mouse that always switched off when
starting the fluorescent tube lighting. Pulling the USB out and back in , restarted it.
Here are my options :
A RC filter after the HC132 to filter out the glitches. Effective , but I don't want a
big delay and if the C is too big , there is no room for a diode to protect the Hcmos
IC. (How big , or how long are glitches caused by fluorescent tube starting ?)
Or at the opto side = the HC 132's input . Again a cap , but not too big that it can
destroy the opto or the cmos input.
I can't go for lower resistors , because of battery power and it would change the
switching levels.
Yes I can experiment , but i've made a very small pcb with all smd's , which makes
it very difficult and big chance of the copper of the pcb coming loose when soldering too often and everything around it becoming too hot again.
So I ask here first , for people's experience with this.
Yes it is not strictly "Power supplies" , but is is to monitor de power supply to my
HP amp. That's why I posted it here. Thanks.
To monitor the dual power rails for my HP amp , I made a simple under and over
voltage detector , which switches off the power (and relay) , and gives an indication of what went wrong.
It works as it should , BUT I noticed when doing tests that it gets triggered by starting a fluorescent tube lighting or touching inputs just with a test lead.
Grounding the inputs without the 47k resistors or connecting the inputs with other
HCmos outputs , no problem , but the problem is now also on the optocoupler's
transistor side. When the opto transistor is off , again triggered by fluorescent tube
lighting starter.
Will encasing it in an Aluminium casing solve this ?
Now I made lots of Cmos devices , never had this problem , but now I live in a
electrosmog environment , with lots of badly laid , overhead power wires and a
nearby WiFi transmitter. I had an computer mouse that always switched off when
starting the fluorescent tube lighting. Pulling the USB out and back in , restarted it.
Here are my options :
A RC filter after the HC132 to filter out the glitches. Effective , but I don't want a
big delay and if the C is too big , there is no room for a diode to protect the Hcmos
IC. (How big , or how long are glitches caused by fluorescent tube starting ?)
Or at the opto side = the HC 132's input . Again a cap , but not too big that it can
destroy the opto or the cmos input.
I can't go for lower resistors , because of battery power and it would change the
switching levels.
Yes I can experiment , but i've made a very small pcb with all smd's , which makes
it very difficult and big chance of the copper of the pcb coming loose when soldering too often and everything around it becoming too hot again.
So I ask here first , for people's experience with this.
Yes it is not strictly "Power supplies" , but is is to monitor de power supply to my
HP amp. That's why I posted it here. Thanks.
Attachments
You might find your problem is fixed more simply by putting resistors in parallel with the LEDs in your optos.
So the opto's leak ? I'm not sure that will solve it . It means the voltage level at the HC132 inputs will be between the 0 and the 5V with the noise superimposed on it , it might make it worse like using an cmos inverter as an amplifier.
No - its not the optos that leak, its the zeners. There's no telling what current they might pass below their zener voltage - the zener voltage is defined at 1mA minimum normally. They also have capacitance in parallel which might be enough to give you a spurious pulse - especially with your 75k load resistors on the opto outputs.
These are very sharp zeners , at 10 to 100 uA they are already at their voltage , no need for 1 mA or more . Note that the zener side doesn't always have a voltage . On standby , the monitoring circuit is powered up , but the 2 times 2x15V of the amp are 0V so the zeners and optoLED have no current. Glitches like the fluorescent tube starter , trigger the indicator flipflops with or without the zener/optoLED side having power, luckily the reset D-flipflop is not triggered on standby other wise I couldn't put the circuit on.
So it's a good sugestion , but I'm sure it's not spurious noise on the zener .
So it's a good sugestion , but I'm sure it's not spurious noise on the zener .
I've not come across zeners which are at their voltage at 10uA before, I shall be interested to check them out. What's the part number? If I were you, I'd lower those 75ks.
TZM5239B : 9,1 V zener in Minimelf : 8,99V @ 10uA 9,08V @ 6mA from vishay .
DL5245B 15 V zener also in minimelf : 15,11 V @ 5uA 15,22 @ 2,5 mA.
Others around the same values , because of tolerance. Those 2 were used.
1N4744 : 15 V , 1,3W 14,85V @ 5uA 14,88 V @ 2,4 mA . Lots of zener are like this. Zeners lower than 6,2 V are less sharp , in my experience and testing.
Lowering the 75k , changes the threshold/switch level.
I have another input with 10k , and it has the same problem . It's also on batteries so I need to keep the power down.
DL5245B 15 V zener also in minimelf : 15,11 V @ 5uA 15,22 @ 2,5 mA.
Others around the same values , because of tolerance. Those 2 were used.
1N4744 : 15 V , 1,3W 14,85V @ 5uA 14,88 V @ 2,4 mA . Lots of zener are like this. Zeners lower than 6,2 V are less sharp , in my experience and testing.
Lowering the 75k , changes the threshold/switch level.
I have another input with 10k , and it has the same problem . It's also on batteries so I need to keep the power down.
> gets triggered by starting a fluorescent tube
> again triggered by fluorescent tube lighting starter.
> an computer mouse that always switched off when starting the fluorescent tube lighting
I've had bad fluorescent starters but that one is the WORST.
Try grounding it with clip-lead. (Do not get killed.)
Try gently taking the fixture to scrap-metal and the tubes to the hazard-waste. LEDs are better, and now cheaper. (Yes they have faults also: I just tossed a "good old" G.E. because I thought it was off; on, but dim.)
> again triggered by fluorescent tube lighting starter.
> an computer mouse that always switched off when starting the fluorescent tube lighting
I've had bad fluorescent starters but that one is the WORST.
Try grounding it with clip-lead. (Do not get killed.)
Try gently taking the fixture to scrap-metal and the tubes to the hazard-waste. LEDs are better, and now cheaper. (Yes they have faults also: I just tossed a "good old" G.E. because I thought it was off; on, but dim.)
^There are 3 of them and they are not mine. I can't replace them . I live in sort of the third world , no grounding wires here.