Spark absorber circuit?...

[gutisie]

Good afternoon All,

My name is Frank, and at the moment I am trying to design a little simple circuit for a spark absorber.

The idea is to conect this circuit between the batery and the circuit to protect (switch).

The circuit has a n/o switch that controls a dc motor.

I have tried mosfets, snubber circuits, spark suppression, but none of them work properly where I want.
they just dont get rid off the spark at the switch.

I supply 11.1 v with a lipo batery. 11.1v 2000mAh 20 C. The motor at peak load may burn 20A.

So I will appreciate any ideas.

Thanks ever so much for your help.

Best regards.
Frank.

 

[MikeMl]

Can you post a circuit which shows the battery, motor, switch, and where you placed the snubber circuit(s)?

 

[gutisie]

Hi Mike,
thanks for the reply, i have posted a picture of the idea, but its being checked apparently.
Best regards.
Frank.

 

[gutisie]

batery positive ----o (here is where i need the spark absorver) o-----o--(switch)n/o ----------motor

negative-----o o---------------------------------motor

I hope this helps.

Best regards.
Frank.

 

[tcmtech]

You would need to have the surge suppressor in parallel with the switch. Usually a simple capacitor with a low ohm resistor is more than adequate for a DC circuit.

Try a 1 uf capacitor with a 10 ohm resistor in series wired across your switch and see if that takes the spark flash down some.

 

[BrownOut]

You might just be getting some inductive kickback from your DC motor. You could try a diode across the motor orented to block normal current ( cathode to "+" supply ) The idea is the diode provides a path for high voltage kickback when the motor is switched off.

 

[gutisie]

thanks all!!!

yeah thats fine, but I can not brake the unit and get to the switch, that is why the need for "something", which I can plug into the batery, before pluging into the device.

Sorry the drawing is not very clear.

Any more ideas?...

 

[tcmtech]

Then you are going to be out of luck being the surge suppression for a switch needs to go across the switch.

Why do you need to protect the switch any way? If its burning out quickly then its being over powered, too much current, and no surge suppression will help that and the only fix using a switch designed for the load being controlled.

 

[BrownOut]

thanks all!!!
Any more ideas?...

Yeah. See post #6. It doesn't require access to the switch.

 

[4pyros]

but I can not brake the unit and get to the switch, that is why the need for "something", which I can plug into the batery, before pluging into the device.

You need to either change the switch or put somthing across the contacts. If you tell us what this is for maybe we can help further.

 

[gutisie]

Yeah. See post #6. It doesn't require access to the switch.

hi, thanks!!

i thought you needed to put the diode between the dc motor and the switch....am i right?..or you meant that i put it in paralell?...

Thanks again.

 

[BrownOut]

Put it in parallel. It should oppose normal current flow -- VCC to the motor. The idea is when the power is disconnected from the motor, A voltage spike can appear at the motor's terminals. The diode allows the current a path so that the spike doesn't build up.

You can also forward bias a diode between the switch and motor, but you'll have ~.7V less at the motor due to the diode's voltage drop.

 

[gutisie]

ok thanks ever so much.

So I will need a zener diode?...of what voltage and w rating?..

suppy voltage is 11.1 dc and motor burns 20 A tops.

thanks again.

Best regards,
frank.

 

[BrownOut]

No, just an oridnary rectifier diode. You might want a fast recovery one, but normally a 4004 or equivilent should work.

 

[gutisie]

ok thanks, i will try that!!
Let's see if it does the trick!!

thanks a lot again.

regards.

 

[BrownOut]

Just make sure you orient the diode so that it opposes the motor drive supply. Otherwise, you short circuit your supply.

 

[gutisie]

Hi thanks.

So pointing from negative to posive?..

Sorry i am useless.....
Thanks.

 

[BrownOut]

If you mean does the arrow of the symbol point negative to positive, then yes.

 

[gutisie]

it didnt work the rectifier.....
I have found this device which you can get and simply connect it to your power supply +ve and -ve.
It would be exactly that thing!! but just the surge protection part of it.
**broken link removed**

Do you know how it works?...do you guys know how to make one of those?..do you know any diagrams, or circuits for it?..

Thanks.
Best regards.
Frank.

 

[tcmtech]

Do you know how it works?...do you guys know how to make one of those?..do you know any diagrams, or circuits for it?..

It probably just a few small capacitors and low voltage MOV's inside. Pretty common electronics parts but it still wont do a thing for your switch.

The problem is the simple physics of if you don't want your switch to arc that energy that makes that spark has to temporarily go some place else in the same circuit that the switch was in.

I have already told you how to do it. The surge suppressor has to be in parallel with the switch. That its nothing else.
A small capacitor and resistor or a MOV in parallel with the switch is all you need providing your switch is capable of handling the currents you are putting through it in the first place.