The bleeder resistance

Just want to hang out with other Makers and chat about stuff? This is the place to do it.
Post Reply
triaco
Posts: 19
Joined: Fri Jan 31, 2014 5:05 am

The bleeder resistance

Post by triaco » Thu Feb 13, 2014 3:42 am

Hi,

I've got a circuit like this:

Image

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

Thank you.

DaveJ
Posts: 9
Joined: Fri Jul 26, 2013 10:03 am

Re: The bleeder resistance

Post by DaveJ » Sat May 24, 2014 12:56 am

The FSS1 relay is a solid state relay. I don't think you would need a bleeder resistor in parallel with it.
This relay doesn't have a coil in it so the transistor doesn't need any protection from high voltage spikes when the relay is switched from on to off. That is when you usually use a bleeder resistor in parallel with a relay.
I am thinking that if you wanted to restrict the current flowing through the relay to 15mA you would use a resistor in series with the relay. at 5v you would use Ohms LAw to work it out E = IxR
therefore 5/0.015 = 330 ohm resistor. That would allow only 15mA to flow through the transistor.
The other way you could do it would be only allow the transistor to conduct 15mA by using the correct base resistor size.

triaco
Posts: 19
Joined: Fri Jan 31, 2014 5:05 am

Re: The bleeder resistance

Post by triaco » Thu Jul 10, 2014 4:03 am

DaveJ wrote:The FSS1 relay is a solid state relay. I don't think you would need a bleeder resistor in parallel with it...
We are talking about two different topics, that in fact are confusing in theory.
In my case, yes you might need that bleeder resistor.
Anyway, I have already TUNED my circuit and runs for months without a hitch.

Image

eric_1050
Posts: 5
Joined: Sat Aug 30, 2014 11:50 am

Re: The bleeder resistance

Post by eric_1050 » Sat Aug 30, 2014 6:34 pm

Hello I know you have your project working,

But you do not need a bleeder resistor in parallel, you need a diode reverse bias across any coil to discharge any high volts back EMF the coil releases when power is removed from the coil, your project might work all right but it is safer to add the diode. In you flick through any project article in a electronics magazine you should see such a diode across any thing that has a inductance load.

To read more on bleeder resistors, where the purpose is used to discharge capacitors AFTER any electronic appliance has been turned off. To read more go to
http://en.wikipedia.org/wiki/Bleeder_resistor and read the part I added in many months ago "Electrical regulations"

angusgr
Freetronics Staff
Freetronics Staff
Posts: 853
Joined: Tue Apr 09, 2013 11:19 pm
Location: Melbourne, Australia
Contact:

Re: The bleeder resistance

Post by angusgr » Mon Sep 01, 2014 12:51 am

Hi eric,

The load in the example shown is the Solid State Relay input which is not inductive like a normal relay coil, therefore no need for a back EMF/flyback diode.

The confusion may arise from the term "bleeder resistor". I think a more suitable term for the schematic shown in this thread is a "pull-up resistor". Thanks for the link to the page with explanation on the bleeder resistor term.


Angus

eric_1050
Posts: 5
Joined: Sat Aug 30, 2014 11:50 am

Re: The bleeder resistance

Post by eric_1050 » Mon Sep 01, 2014 1:25 am

Yes I had no idea what is inside the square box, the Impedance given distorted my response.


Post Reply

Who is online

Users browsing this forum: Bing [Bot] and 4 guests