[SOLVED] The bleeder resistance

hello,

I've got a circuit like this:



My question is how can I match the bleeder resistor at BEST ?
There are formulas for that, but with my Fluke 105 I can forget it; leakage current required etc...

Thank you.

That resistor is not a bleeder. A "bleeder" resistor is fitted across the terminals of a high voltage capacitor, so its stored charges can be bled away, leaving the capacitor safely discharged.
That resistor is called the "collector load" and you don't need it in this circuit, the input of your FSS1 will act as a load.
Frank

I was saying bleeder resistance
I saw the commercial relay board and there is a such resistor

Below we have mention the bleeder resistance issue on page C-341:

https://www.omron.com/ecb/products/pdf/precautions_ssr.pdf

I am trying to tune my circuit so SSRs will live longer and happier.

SSR leakage current is flowing through switched load when SSR is OFF. It has nothing to do with input of SSR. What is your Omron article talking about is leakage current of transistor used to control SSR. This is Ice0 current when transistor is OFF. Your bleeder resistor must be so small that Rbleed*Ice0 is smaller than 1V which is condition for SSR to go OFF. Follow the article.

Datashet for BC547B contains data for Icb0. Roughly, Ice0=Icb0*Hfe. That parameters are changing with temperature and consider worst case.
If the transistor leakage current is smaller than 2mA you do not need bleeder resistor.

BTW fss1-102z/5v SSR is opto isolated and no current from secondary can flow to input trigger circuit.

SSR leakage current is flowing through switched load when SSR is OFF. It has nothing to do with input of SSR.

Click to expand...

Where did I say it ? I know that.

Follow the article.

Click to expand...

That's why I posted this tread 'cos I follow the article,
I saw similar commercial circuit, but with different SSR, and it has 150 Ohm resistor on inputs.

Datashet for BC547B contains data for Icb0. Roughly, Ice0=Icb0*Hfe. That parameters are changing with temperature and consider worst case.
If the transistor leakage current is smaller than 2mA you do not need bleeder resistor.

Click to expand...

I will not be able to make a proper measurements with battery powered multimeter.

I might leave that 180 resistor where is it, as it gives me 2/3 current of SSR (15 is MAX). With 120 ohms I had reading of 8.75mA.
The circuit in first post works very well, had no issue with triggering the load ON/OFF.


Thank you.

chuckey said:

That resistor is not a bleeder. A "bleeder" resistor is fitted across the terminals of a high voltage capacitor, so its stored charges can be bled away, leaving the capacitor safely discharged.

Click to expand...

That's my understanding, but several articles use the term;

FAQ No. FAQ02155
Related Contents
Primary Contents
Question
The Solid-state Relay does not turn OFF. What is causing this and what can be done about it?
Answer

There may be separate causes for the input side and the output side. The following provides separate explanations.
Input Side:
1.Leakage current of the drive circuit on the input side may be causing a reset failure. Insert a bleeder resistor as a countermeasure.

Connect a bleeder resistor as in the figure above and set the bleeder resistance value so that the Solid-state Relay input voltage is 0.5 V max. when the Solid-state Relay is OFF.

Unless you can measure the leakage current, you just have to experiment - maybe start with 2k2 and work your way down.

kam1787 said:

Connect a bleeder resistor as in the figure above and set the bleeder resistance value so that the Solid-state Relay input voltage is 0.5 V max. when the Solid-state Relay is OFF.[/I][/B]

Unless you can measure the leakage current, you just have to experiment - maybe start with 2k2 and work your way down.

Click to expand...

kam1787,Thank you very much.
You've just gave me an alternative method to find a match.
Finally , that's what I asked.
People rush with answers, and end up off topic, or lectures.

Transistor leakage current can be measured with multimeter. Disconnect SSR and on it's place connect ampermeter. Ensuring that transistor is OFF switch on power supply and measured current is leakage current of transistor. You should heat up transistor to see the current change or wors case.
Sorry I upset you with unnecessary remark on leakage current.