How is it possible to produce a 5 Farad capacitor for $50, let alone one that weighs in at 5lbs and has a blue led display for the "power" available to the amplifier at any given time. What is this?
Amazon.com: PYLE PLCAPE50 5.0 Farad Digital Power Capacitor: Electronics
Amazon.com: PYLE PLCAPE50 5.0 Farad Digital Power Capacitor: Electronics
It is a "stiffening capacitor". It is used in auto sound applications where the pulses of current drawn by a 1.21 jiggowatt subwoofer cause problems with the cars electrical system. The capacitor goes across the 12 volt supply right at the amplifier and provides energy storage to supply the amplifier when the bass note goes THUMP! Based on the size I think the 5 Farad rating may be a bit optimistic.
Due to the large number of thumpa thumpa cars in the south Florida area, even Walmart sells these things. The one I got at Walmart is 2 Farads, just the cap, no case, no LEDs. It looks just like a big fat electrolytic cap except the usual blue shrink wrap is silver. Why did I buy one? It fixes the havoc that a 100watt ham radio in SSB mode caused on the electronics in a Toyota pickup truck.
Digital in the name worries me, it could be something strange like a 5000uF 450V capacitor and some form of up / down converter, not much use if that is the case as the ESR would be high. The stupid thing is that best place for capacitance in on the amplifier supply rails not the feed to the amplifier PSU.
FWIW it is an Amazon special price with the normal price nearer $75 and capacitors have shrunk quite drastically in the past 10 years.
FWIW it is an Amazon special price with the normal price nearer $75 and capacitors have shrunk quite drastically in the past 10 years.
The electronic goldmine has a bunch of ultracaps on sale now if you feel like messing around with them - 30 bucks will get you a 3000F (yeah, 3 thousand farads) 2.7V cap that is very good at vaporizing wire and such. They sell smaller (2600F I think) ones as well for even cheaper. I bought a few of the bigger ones figuring someday I'll come up with a cool use for them.
there are reasons why you wouldn't want to use caps like this in a home supply. 1- the voltage rating is low. these are designed for 12-15v. 2- the start up current is MASSIVE! you have to charge these things up with a light bulb before connecting them or the arc like a mother! 3- massive strain on a bridge rectifier 5- slow discharge when compared to a bank of smaller caps = the the same uf etc etc etc.
Like tubelab said. these stiffening caps help with those kids and there jiggawatt stereos. its amazing just how much current those boom box amps really draw. I am adding a small but high quality amp set up to my car with a 375w amp for the subs and at full power it draws almost 50 amps! (it will never see full power in my car but...) add to that a 4x75w amp for the 4 corners that draws about the same current and that is a max of 100amps! and thats SMALL stuff. these days kids have amps that are in the KW range!
so you could potentially have 75-100amp peaks hanging off the end of 15-20' of 8ga maybe 4ga wire if you can afford it. the voltage sag is huge. these big fat caps help hold up that end of the line for those short duration peaks.
I have been curious if they really are what they say they are. I picked up a pair of 1F caps at a swap meet for $10 and they do run a .5amp light bulb for a considerable amount of time. I need to figure out the RC time constant and see if i can calc what the real capacitance is.
Like tubelab said. these stiffening caps help with those kids and there jiggawatt stereos. its amazing just how much current those boom box amps really draw. I am adding a small but high quality amp set up to my car with a 375w amp for the subs and at full power it draws almost 50 amps! (it will never see full power in my car but...) add to that a 4x75w amp for the 4 corners that draws about the same current and that is a max of 100amps! and thats SMALL stuff. these days kids have amps that are in the KW range!
so you could potentially have 75-100amp peaks hanging off the end of 15-20' of 8ga maybe 4ga wire if you can afford it. the voltage sag is huge. these big fat caps help hold up that end of the line for those short duration peaks.
I have been curious if they really are what they say they are. I picked up a pair of 1F caps at a swap meet for $10 and they do run a .5amp light bulb for a considerable amount of time. I need to figure out the RC time constant and see if i can calc what the real capacitance is.
Cornell Dubilier makes somewhat similar.
In regard to the application - just read the datasheet.
Do not use flash type caps - they are not designed to withstand
voltage applied for prolonged period of time.
Well, what flash operates from 12 VDC?! LED... based...
Price seems to be too low: decent 3"x6" power lytic costs
at least 50% more.
Please pay attention to the manufaturing date - they may dry out.
In regard to the application - just read the datasheet.
Do not use flash type caps - they are not designed to withstand
voltage applied for prolonged period of time.
Well, what flash operates from 12 VDC?! LED... based...
Price seems to be too low: decent 3"x6" power lytic costs
at least 50% more.
Please pay attention to the manufaturing date - they may dry out.
The big cap I got from Walmart says 2F 16V right on it. So you might be able to use it in a 12 volt power supply if the surge and start currents are dealt with.
I don't know where that quote came from but I did use a pair of 375 volt photoflash caps in series in a tube amp about 10 years ago. They worked fine for about 6 years and then one of them just decided to spew its guts all over the inside of the amp. Each cap saw only 200 volts and there were equalizing resistors across the caps.
Most camera phones use a multi chip LED for the flash. Peak current is in the 1/2 amp range. That is usually provided by the phones battery and a ceramic or tantalum cap in the 50uF range.
It was a joke about LED flash... I would of used HV cap, switch, step down pulse transformer...
From my experience, photoflash caps:
a) do not tolerate ripples i.e. AC current
b) need to be formed if not used more often than "normal" ones
c) do not stand being charged for long time - usually get quite hot
"b" probably was a cause of blow-up.
As we all know, unformed caps draw up to few amps (initially) if voltage applied.
One cap should of had higher leakage than the other - equalizer was of no help.
From my experience, photoflash caps:
a) do not tolerate ripples i.e. AC current
b) need to be formed if not used more often than "normal" ones
c) do not stand being charged for long time - usually get quite hot
"b" probably was a cause of blow-up.
As we all know, unformed caps draw up to few amps (initially) if voltage applied.
One cap should of had higher leakage than the other - equalizer was of no help.
My guess is that one of the caps shorted first, then the other had to eat 400 volts of B+ for an unknown period of time.
I built the push pull 300B tube amp as an experiment. It used 100% junkbox parts except for the tubes. The amp worked far better than I had expected and resisted all attempts to upgrade anything to better quality parts. It sounded worse so I always went back to the original configuration. I used some hamfest sourced photoflash caps because I had them. There were two in series in a choke input configuration (low ripple current).
The amp worked flawlessly for several years and saw a lot of use. In the last year of its life it developed a background noise in one channel and developed a habit of popping the line fuse every once in a while. The power is very dirty here in the summer so I ignored it. One of the caps had probably shorted. They were under the chassis so I didn't notice if they were hot. There was no smell of venting. Then one day.....Pffffft...bang....silence. The non exploded cap measures 10 ohms, the gooey mess measures in the thousands, two of the 4 diodes are shorted.
The amp has grown a spot in my closet for a couple of years waiting for me to rebuild it.
I tossed the other photoflash caps that I got from the hamfest that day but... I have a friend that used the same caps form the same hamfest in a ham radio RF amplifier. I don't know how many he wired together but his B+ voltage is about 1800 volts and the amp is still running!
I built the push pull 300B tube amp as an experiment. It used 100% junkbox parts except for the tubes. The amp worked far better than I had expected and resisted all attempts to upgrade anything to better quality parts. It sounded worse so I always went back to the original configuration. I used some hamfest sourced photoflash caps because I had them. There were two in series in a choke input configuration (low ripple current).
The amp worked flawlessly for several years and saw a lot of use. In the last year of its life it developed a background noise in one channel and developed a habit of popping the line fuse every once in a while. The power is very dirty here in the summer so I ignored it. One of the caps had probably shorted. They were under the chassis so I didn't notice if they were hot. There was no smell of venting. Then one day.....Pffffft...bang....silence. The non exploded cap measures 10 ohms, the gooey mess measures in the thousands, two of the 4 diodes are shorted.
The amp has grown a spot in my closet for a couple of years waiting for me to rebuild it.
I tossed the other photoflash caps that I got from the hamfest that day but... I have a friend that used the same caps form the same hamfest in a ham radio RF amplifier. I don't know how many he wired together but his B+ voltage is about 1800 volts and the amp is still running!
I have measured some before. The older ones (from when things are made as they said they were in the spec sheet, this was a white EFX cap) 1F caps did measure 1F. the newer ones measured at 0.85F for the 1F ones (the brands I checked are cheap asian imports and one EFX cap with the silver and blue wrapping)
I have not been actively building amps for 25years and used to know a number of surplus electronics companies and Ham Fests that reliably had very good computer grade power supply caps cheap. This was when everything was changing to low voltage for the "new" digital equipment. It was typical to find big blue Sprague's for $5.
Other than monitoring Ebay what are some good resources for 30V-80V cans with lots of zero's behind the first couple numbers?
Other than monitoring Ebay what are some good resources for 30V-80V cans with lots of zero's behind the first couple numbers?
Hi Bruce,
Wow, 5 Farads - quite the monster! It might not be all bad, actually.
I work in electronics - not in component design, but I know a little about caps. From what I've heard, if you want to make a high-value capacitor, you need either a good quality electrolyte material, or lots of surface area for both plates (physically big cap) or both.
One way to build a big mean cap for not a lot of money is to choose a lower quality electrolyte material, and then make up for it by just making massive electrode plates. This could be made of aluminum foil, rolled up like a fruit roll-up with the electrolyte in between.
Now if you factor in high production-volume manufacturing, the cost to produce drops even further. So much so that you can throw in nice things like flashy lights (even though I know better, I am a fan of flashy lights!).
The down sides of going with a cheaper electrolyte include not the best tolerance over temperature performance (as the temperature changes, the thing might wander by as much as 25% around 5 farads), and poor frequency performance (high frequency ripple may just run straight past as the slow moving dipoles in the low quality electrolyte can't change direction fast enough).
Those 2 down-sides aren't really a big deal for this application though, so such a cap might be a pretty good deal. As someone else mentioned, it's main job is to handle high-current pulses required for phat beats. These pulses are relatively slow moving, and can be leveled off nicely with a big bucket of capacitor such as this.
One other down-side of a cheaper electrolyte is long-term reliability. If they did in fact save a few bucks by using a cheaper electrolyte, the value may degrade over a couple of years or so. Still, for that application it might be an ok deal!
Jim
I am not much acquainted with electronics. But I can solder and follow directions. I can check only for continuity and might as well try to read hieroglyphics as look at an oscilloscope. I am solemnly sworn not to power anything until it has been checked by those whose acquaintance with electronics makes things work safety.
I have been intrigued with the Hiraga Super Class A and sort of understand how it works. The build I like is very elegant, in a brutish sort of way.
The capacitor bank consists of six 220000 uF capacitors (how do you spell 1.2 Farads?). These puppies are not inexpensive, but it is fun going on the dumpster scavenger hunt. Wish me luck.
Jean Hiraga's Super Class-A Amplifier
I have been intrigued with the Hiraga Super Class A and sort of understand how it works. The build I like is very elegant, in a brutish sort of way.
The capacitor bank consists of six 220000 uF capacitors (how do you spell 1.2 Farads?). These puppies are not inexpensive, but it is fun going on the dumpster scavenger hunt. Wish me luck.
Jean Hiraga's Super Class-A Amplifier
The PSU in the link uses a crude brute force approach to achieve low ripple, If I was designing that I would be looking at some other options, Choke, input filter, Pi filter, capacitance multiplier and series pass regulator.
If you are on a dumpster hunt, chokes turn up with remarkable frequency on power electronic equipment these will reduce the size of the capacitors required for any given ripple. If you choose the right dumpster, power transformers and heatsinks will also be found. I got a 1.2Kva 52V transformer recently and 3 0.25 C/W heatsinks (Big enough for most class A applications) from a scrapyard. I don't mind paying $4 / kg for heatsinks and transformers. I missed out on 30 2000uF 500V capacitors from the same scrapyard
If you are on a dumpster hunt, chokes turn up with remarkable frequency on power electronic equipment these will reduce the size of the capacitors required for any given ripple. If you choose the right dumpster, power transformers and heatsinks will also be found. I got a 1.2Kva 52V transformer recently and 3 0.25 C/W heatsinks (Big enough for most class A applications) from a scrapyard. I don't mind paying $4 / kg for heatsinks and transformers. I missed out on 30 2000uF 500V capacitors from the same scrapyard
For those of you, who like myself, are unaware of recent capacitor technology. The stuff about ultra caps is near the end
Ultracapacitors Challenge the Battery
Just went back and saw that was written in 2004 so not that recent.
Ultracapacitors Challenge the Battery
Just went back and saw that was written in 2004 so not that recent.
Looks like a battery but its a cap?
Electric double-layer capacitor - Wikipedia, the free encyclopedia
I guess this new technology is 50 years old. Heres all the gory details.
Electrochemistry Encyclopedia -- Electrochemical capacitors
Electric double-layer capacitor - Wikipedia, the free encyclopedia
I guess this new technology is 50 years old. Heres all the gory details.
Electrochemistry Encyclopedia -- Electrochemical capacitors
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