Hi Andrew ,
100k is paired with 22uf bipolar, but there is 91k serially connected to ground ,so don't what if for ,whether it's to be taken to be in calculation
47 uf paired with 56 k with for 3 seconds delay , matching your calculation,
May minek 123 explain you better
As I said donot know how to calculate but observing multiple circuits using 1237, my guess is as you decrease resistor value the the Tigger voltage decreases,
100k is paired with 22uf bipolar, but there is 91k serially connected to ground ,so don't what if for ,whether it's to be taken to be in calculation
47 uf paired with 56 k with for 3 seconds delay , matching your calculation,
May minek 123 explain you better
As I said donot know how to calculate but observing multiple circuits using 1237, my guess is as you decrease resistor value the the Tigger voltage decreases,
You are right, it's missing
I forgot about it...
Well, it works without it.
hi minek123,
finished the speaker protect as shown with 12v, seems to be working( do not how to test it) , i have few doubts about ground reference,
suppose if iam powering it from separate power supply ( either via 220 v to 12v dc converter or via 12 v transformer out put) will the board needs ground from star ground or its just needs only its power ground hope u understand my question , can u tell me in detail how to test it
hi, cakyol
i have built it and its working but i have not able test inside an amplifier as my
other projects got derailed due to other factors,
if you are interested i can provide gerber files for you to manufacture as sending pcb might not be viable option from india to usa due to customs forms
Anyone know what value of series resistors for the DC sensing to use with a power amp with 95 volt rails.
The 1237 is powered by a 12 VDC supply and delay and shutoff work fine, i just need to figure out what value the 2 resistors that sense the DC offset are ? Can’t tell from the data sheet. pin 2 has 100 uf bipolar cap and a 100 k to ground, but I can t figure out the resistors from the amp output to pin 2 to sense the DC with the chance it goes to 95 VDC
The 1237 is powered by a 12 VDC supply and delay and shutoff work fine, i just need to figure out what value the 2 resistors that sense the DC offset are ? Can’t tell from the data sheet. pin 2 has 100 uf bipolar cap and a 100 k to ground, but I can t figure out the resistors from the amp output to pin 2 to sense the DC with the chance it goes to 95 VDC
I am trying to understand this a bit better.
Pin 2, which detects the DC offset, have wildly varying capacitor values based on different designs, altho most of the other components are pretty similar.
What should that value ideally be ?
In my estimate, if it is too small, it seems like it will trigger prematurely at lower frequencies. So, to allow a 5 Hz signal to go thru without firing, what should the approximate value be ?
I have seen values ranging from 22uF all the way to 330 uF.
Has anyone actually experimented with it ?
Assuming Ra, Rb & Rc are 120k, 120k & 91k as shown on the datasheet calculations (2V threshold), what should the C be so that it does not fire above 5Hz during normal operation. My choice of 5Hz seems random but it is possible to have low frequency coming into the speaker because of source, even tho the speakers cannot reproduce it. So, the circuit must not trigger and keep on cutting the speaker off when there is no actual real danger to it.
Last edited:
