Me again...filter question

[newbie]

OK I asked a question about using a choke as a filter a few weeks back, I am about to update the PCB with this filter

I have the main feed in then a 0.2uf ceramic cap then a 220uf cap then the 33uh choke.

I think this is all OK but my question is about the 220uf cap, should it be ceramic or electrolytic?

This is for a car / truck (12-24v)

Thanks
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This message was ported from CCS's old forum
Original Post ID: 9597

[john lee]

:=OK I asked a question about using a choke as a filter a few weeks back, I am about to update the PCB with this filter
:=
:=I have the main feed in then a 0.2uf ceramic cap then a 220uf cap then the 33uh choke.
:=
:=I think this is all OK but my question is about the 220uf cap, should it be ceramic or electrolytic?
:=
:=This is for a car / truck (12-24v)
:=
:=Thanks
Hi, I am John,
Ref: cap:
Ceramic in a truck!(definitely).Also wise to stick a 5-volt Zener in the line, to un-spike the dirty juice from the crappy alternator.Maybe set fuses NOWDT,NOBROWNOUT,Until U get it bugless.
Regards,
John Lee.
England.
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This message was ported from CCS's old forum
Original Post ID: 9607

[newbie]

OK so we are saying ceramic not electrolytic.

I am fairly new to electronics when you say stick a zener in line, what do you mean exactly, cathode to +ve and anode to GND?

Sorry for being stupid.



:=:=OK I asked a question about using a choke as a filter a few weeks back, I am about to update the PCB with this filter
:=:=
:=:=I have the main feed in then a 0.2uf ceramic cap then a 220uf cap then the 33uh choke.
:=:=
:=:=I think this is all OK but my question is about the 220uf cap, should it be ceramic or electrolytic?
:=:=
:=:=This is for a car / truck (12-24v)
:=:=
:=:=Thanks
:=Hi, I am John,
:=Ref: cap:
:=Ceramic in a truck!(definitely).Also wise to stick a 5-volt Zener in the line, to un-spike the dirty juice from the crappy alternator.Maybe set fuses NOWDT,NOBROWNOUT,Until U get it bugless.
:=Regards,
:=John Lee.
:=England.
___________________________
This message was ported from CCS's old forum
Original Post ID: 9609

[john lee]

:=OK so we are saying ceramic not electrolytic.
:=
:=I am fairly new to electronics when you say stick a zener in line, what do you mean exactly, cathode to +ve and anode to GND?
:=
:=Sorry for being stupid.
:=
:=
:=
:=:=:=OK I asked a question about using a choke as a filter a few weeks back, I am about to update the PCB with this filter
:=:=:=
:=:=:=I have the main feed in then a 0.2uf ceramic cap then a 220uf cap then the 33uh choke.
:=:=:=
:=:=:=I think this is all OK but my question is about the 220uf cap, should it be ceramic or electrolytic?
:=:=:=
:=:=:=This is for a car / truck (12-24v)
:=:=:=
:=:=:=Thanks
:=:=Hi, I am John,
:=:=Ref: cap:
:=:=Ceramic in a truck!(definitely).Also wise to stick a 5-volt Zener in the line, to un-spike the dirty juice from the crappy alternator.Maybe set fuses NOWDT,NOBROWNOUT,Until U get it bugless.
:=:=Regards,
:=:=John Lee.
:=:=England.
Hi,
Assuming You are using some form of voltage regulator, eg 7805, or similar, you can get electrical noise, which the cap should absorb. An electrolytic is liable to spontaneous breakdown depending on age, so the ceramic is the better option.In case the voltage reg dies, as alternators sometimes go crazy, You could fry the PIC, so as a backup, a 5 volt zener will keep the volts stable.Zeners themselves generate white noise, so a small(about100nf)cap is connected after the zener, from Vcc to Vss.The end of the zener with the ring around it goes to the +ve rail. Just ensure the power rating is adequate.OK??
Regards,
John Lee.
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This message was ported from CCS's old forum
Original Post ID: 9620

[Hans Wedemeyer]

:=I think this is all OK but my question is about the 220uf cap, should it be ceramic or electrolytic?

Sounds like you are trying to limit spikes.

If you could buy a "ceramic 220uf cap", it would have to be at least 35-50V rating to work in a 24V system.

I may be out of touch but a "ceramic 220uf cap" at 35V would be difficult to find !

Someone suggested putting a zener in the system. Well a plain out zener will be far too slow to chop spikes.
You could look at a P6KE30C or CA it is similar to a zener except it is designed to chop spikes. The 30 in that part number refers to 30 Volts. The PK6E is rated to 1500Watts for some microseconds. As most vehicle type spikes are very fast it will munch them down to the reated voltage and prevent you system from burning up.

BAT. + ------- COIL ----------------
| |
P6KE30C LOAD or your PIC project
| |
BAT. - -----------------------------

Place the P6KE after the coil, that way it has something to pull down against.

The comment about white noise is irrelevant, in this situation the white noise is far less than the noise from the vehicle's generator, anyway the white noise only happens when the Zener goes start to avalanche....

Good luck....

Please read this link, you questions are getting off topic....









Please read the Off Topic link....
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This message was ported from CCS's old forum
Original Post ID: 9624

[Sherpa Doug]

:=I have the main feed in then a 0.2uf ceramic cap then a 220uf cap then the 33uh choke.
:=
:=I think this is all OK but my question is about the 220uf cap, should it be ceramic or electrolytic?

A ceramic 220uF cap is going to be very big and expensive, on the order of US$100, a few ounces, and as big as a walnut! The 0.2uF cap is meant to take care of high frquency stuff. The 220uF only has to deal with low frequency, so an electrolytic will be fine.

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This message was ported from CCS's old forum
Original Post ID: 9626

[john lee]

:=:=I think this is all OK but my question is about the 220uf cap, should it be ceramic or electrolytic?
:=
:=Sounds like you are trying to limit spikes.
:=
:=If you could buy a "ceramic 220uf cap", it would have to be at least 35-50V rating to work in a 24V system.
:=
:=I may be out of touch but a "ceramic 220uf cap" at 35V would be difficult to find !
:=
:=Someone suggested putting a zener in the system. Well a plain out zener will be far too slow to chop spikes.
:=You could look at a P6KE30C or CA it is similar to a zener except it is designed to chop spikes. The 30 in that part number refers to 30 Volts. The PK6E is rated to 1500Watts for some microseconds. As most vehicle type spikes are very fast it will munch them down to the reated voltage and prevent you system from burning up.
:=
:=BAT. + ------- COIL ----------------
:= | |
:= P6KE30C LOAD or your PIC project
:= | |
:=BAT. - -----------------------------
:=
:=Place the P6KE after the coil, that way it has something to pull down against.
:=
:=The comment about white noise is irrelevant, in this situation the white noise is far less than the noise from the vehicle's generator, anyway the white noise only happens when the Zener goes start to avalanche....
:=
:=Good luck....
:=
:=Please read this link, you questions are getting off topic....
:=
:=
:=
:=
:=
:=
:=
:=
:=
:=Please read the Off Topic link....
Hi, The Zener is not intended to chop spikes,That is the task of the Choke and Cap.The Zener's task is to simply protect the PIc when the 7805 dies.The 100nf cap is to kill the white noise when the Zener dumps.Ref the "220 Uf Cap", I read "220 Nf", as a 220 Uf would hardly fit in a suitcase.Electrolytics are for use in throw-away equipment, but,in a "fit and forget" application, such as a vehicle,Only an idiot would use electrolytics.
Sincerely,
John Lee.
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This message was ported from CCS's old forum
Original Post ID: 9633