They are also handy if you are not sure if the IC will survive your soldering

Yessirinddeedy

 

I do not want my 555 to end up like my cooking. Ruined by too much heat.

Just a quick question, I am looking around for the parts but I am very confused by the meaning of "low impedance" it is ambiguous at best. I think the word I am looking for is to be able to quantify it. I think it is measured in ohms but google has not been my friend.

It says I need: 100 uF 16 V Electrolytic low impedance type.

I am simply attempting to get the concept right in my head, by using multiple smaller capacitors in parallel is this comparable to using batteries in parallel where each battery receives less strain? So I could simply put multiple 100uf 16v capacitors in parallel to solve this problem?

Hopefully I made sense, my brain is fried a bit like that 555 chip will inevitably become.

 

Don't feel alone in your confusion.
This PDF article should help clear things up:
http://www.illinoiscapacitor.com/pdf/Papers/low_ESR_fact_or_fiction.pdf
Various types of low-ESR caps:
http://www.e-sonic.com/whatsnew/emag2004_3/emag_Passive_nic.pdf
Some interesting history behind electrolytic caps:
http://en.wikipedia.org/wiki/Electrolytic_capacitor
Vishay's low-ESR products:
http://www.vishay.com/capacitors/low-esr/

 

So I could simply put multiple 100uf 16v capacitors in parallel to solve this problem?

If you connect 10 10uF 16V capacitors in parallel, you will have a 100uF 16V with theoreticaly 1/10 of the individual ESR. But maybe 3 or 4 is enough, you need to know what ESR your caps have and what ESR the low-esr types have.

 

Thank you for the replies.

Yet more questions. No don't run away!

I am trying to understand why the components working together do what they do; however I am still finding it quite confusing, it makes sense in some ways but not in others. This has not been helped by websites contradicting each other; particularly when it comes to polarity in diagrams. Some seem to do things backwards. Is it just me or is there a lack of standardised rules when it comes to explaining circuits and diagrams?

I am working from the 12v desulfator diagram here http://alton-moore.net/graphics/desulfator.pdf . If I am correct everything left of the P mosfet is concerned with the 555 which gives timed pulses which tells the mosfet when to conduct. The power comes out the positive red lead of the battery into what will be the top right of the diagram and current goes strait through c4 and charges it and continues through L2 charging that as well while the mosfet is in its non conductive state. When the mosfet becomes conductive the current from c4 pours into L1 charging the inductor and continues round and goes strait back into c4 in a constant loop. When the mosfet returns to its non conductive state the current in L1 can not continue its loop and resists the change in current causing a power spike to be forced through the D1 diode strait into the negative terminal of the battery at the bottom right of the diagram. I can think of a few configurations in which the circuit may function but the description in the documents does not quite seem logical to me. Where am I going wrong?

I am going to the library in a few days to look for some electronics books so hopefully they will help expand my knowledge greatly over time.

As for the low inductance capacitors I am considering this one: http://uk.farnell.com/panasonic/eee...ssellid=9695958&crosssell=true&in_merch=true& I have read that going to a much higher than required voltage for capacitors is a good idea. I am been rummaging through my parts and have found a 100uh 400v capacitor that seems to be in perfect condition that may be an alternative despite being a massive. 2.5cm in diameter and 3cm high not including pins.

 

Thank you for the replies.

Yet more questions. No don't run away!

Usually it's the other guy who runs away.

I am trying to understand why the components working together do what they do; however I am still finding it quite confusing, it makes sense in some ways but not in others. This has not been helped by websites contradicting each other; particularly when it comes to polarity in diagrams.

We'll try to keep you on the straight and narrow path here.
There are many sites that feature electronic schematics; some are very good, some are mediocre, and some are just downright awful. We're aiming for "well above mediocre" here.

Some seem to do things backwards. Is it just me or is there a lack of standardized rules when it comes to explaining circuits and diagrams?

There are a number of standards, unfortunately. In the early days (I'm talking 1960's when consumers first had access to them), PNP transistors were all in vogue, and schematics were drawn differently. It took a decade or so for NPN transistors to really start catching on. Nowadays, N-ch MOSFETs and IGBT's are in vogue, because it was finally realized that electron flow was far more efficient than hole flow. So, schematics were "flipped" upside down; the polarities swapped and the transistor types changed. I had a hard time with NPN transistors after first working with PNP transistors almost exclusively; I didn't "trust" the "newfangled" things.

Alaistair Couper's design uses a P-channel MOSFET, and seems rather upside-down from todays' conventions; however it does work.

I am working from the 12v desulfator diagram here http://alton-moore.net/graphics/desulfator.pdf .

Here's just the schematic excerpted from the document:

If I am correct everything left of the P mosfet is concerned with the 555 which gives timed pulses which tells the mosfet when to conduct.

That's basically correct.

The power comes out the positive red lead of the battery into what will be the top right of the diagram and current goes straight through C4 and charges it and continues through L2 charging that as well while the mosfet is in its non conductive state.

That's not quite correct.
Initially, C4 is charged via the positive side being connected to the positive battery terminal, and it's negative side being connected to the negative battery terminal via L2. Once it is charged, current flow through L2 ceases for a brief period. These are the only charge paths for C4.

When the MOSFET becomes conductive the current from C4 pours into L1 charging the inductor and continues round and goes strait back into C4 in a constant loop.

No.
The voltage across C4 starts current flowing through L1 when the MOSFET turns on. As L1's current builds, current through L2 starts building again to replenish C4.

When the MOSFET returns to its non conductive state the current in L1 can not continue its loop and resists the change in current causing a power spike to be forced through the D1 diode straight into the negative terminal of the battery at the bottom right of the diagram.

That's about it. Inductors are like inertia; they resist change in current. Except you're thinking that C4 is a "loop" - it's a capacitor; a place to store electromotive force - like a bucket is a place to store water.

I can think of a few configurations in which the circuit may function but the description in the documents does not quite seem logical to me. Where am I going wrong?

It's OK to have doubt. I hope I've explained it enough so far.

I am going to the library in a few days to look for some electronics books so hopefully they will help expand my knowledge greatly over time.

See if you can find books by Horowitz; "The Art of Electronics"

As for the low inductance capacitors I am considering this one: http://uk.farnell.com/panasonic/eee...ssellid=9695958&crosssell=true&in_merch=true& I have read that going to a much higher than required voltage for capacitors is a good idea.

The cap is OK. Using caps that are far above the required voltage carries an ESR penalty. You should be looking for caps that are in the 65v to 100v range that are low-ESR.

I am been rummaging through my parts and have found a 100uh 400v capacitor that seems to be in perfect condition that may be an alternative despite being a massive. 2.5cm in diameter and 3cm high not including pins.

It's probably rather high in ESR, and will not likely be a good candidate for this project.

 

Thank you for the reply and explination. I was a bit worried I would just get laughed at. It is good to know where I am going right and wrong. Clearly a firmer grasp of how the components work is needed. Well that is for future study.

I was thinking that 50v would be more than enough as the schematic stated only a 16v one is needed but seeing as the desulfator gives off 60v It is logical that over 60v is a safer area.

What is the technical name of the wire used for inductors that looks like copper with a very thin layer of some kind of insulator? All my searches show up is normal thickly coated wire.

 

Thank you for the reply and explination. I was a bit worried I would just get laughed at.

You shouldn't worry about that. This forum is oriented towards helping "newbies" to intermediate electronic enthusiasts understand circuits better.

It is good to know where I am going right and wrong. Clearly a firmer grasp of how the components work is needed. Well that is for future study.

Have you tried reading through our E-books? There are links to the chapters at the top of every page on the forums.

I was thinking that 50v would be more than enough as the schematic stated only a 16v one is needed but seeing as the desulfator gives off 60v It is logical that over 60v is a safer area.

The voltage across C4 should never exceed 16v. The spikes are isolated from the cap by the 1,000uH inductor.

What is the technical name of the wire used for inductors that looks like copper with a very thin layer of some kind of insulator? All my searches show up is normal thickly coated wire.

Its' generic name is "magnet wire".
http://en.wikipedia.org/wiki/Magnet_wire

 

To be honest I find it difficult to read large amounts of text on a pc screen. I first discovered this site and saved the link because of the guides just to quickly looks through quite some time ago. I only recently ventured onto the forums.

The only thing that is really missing from my project design is the power supply. I have begun a topic on it if anyone is interested: http://forum.allaboutcircuits.com/showthread.php?t=49623

It is amazing how difficult these things can be if you do not know what to even search for to find out. My guess is: it got its name from first being used in electromagnets. *goes to find out if that is true*

 

Hello, a little while has passed since I last replied, I have been reading up on electronics and been looking into a charger for my desulfator. Not to mention the parts have begun arriving.

Just a few questions about my DIY inductors. I have measured been testing out my inductance meter and the results of a few of my inductors are interesting; most have an inductance of only about 50uf which is far less than is needed. Two may be of use. The first is 3300uh and can be seen in the image on the previous page and recognised by the toroid core being in no way visible through the wire. Seeing as it could be a choke core for L2, would a higher uf be an advantage? If not the wire can easily be removed until I get the desired uh. The second is the small black toroid, I have practised winding them with wire salvaged and seem to be able to reach 220uh in only 8 passes through the core of the black one, this seems too few for the inductor to function properly. I estimate that It would need about 60 turns with a yellow inductor core, more wire than I have would be needed and I can only find sellers who sell in bulk, of high amp wire. Should I use the small black toroid with only 8 passes or would it be better to invest in a daft amount of magnet wire?

It is weird that I am a bit excited about building this thing. Very geeky! haha

 

Did you download the "Mini-Ring Core Calculator" that I mentioned in post #17?

It will be very helpful in determining the number of turns you'll need on your toroids to arrive very close to the desired values.

Measure the toroid you're testing for ID, OD, and thickness (height) in mm.
Wind on 20 turns of wire, and check the inductance.
Start the Mini-Ring Core Calculator tool.
Click on the "Unknown Cores" tab.
Then click on the RL?u icon below "info" on the menu bar.
Fill in the turns, inductance measured, OD, ID, and height.
Copy down the numbers you get, and then close that box.

Then, fill in the inductance you want, and then click "Copy AL from tool" - you'll see the number of turns you'll need to get the value you want. If you entered the dimensions of the toroid accurately, you'll get the length of wire that is required to place that many turns on the toroid. Always add several inches.

50uH would be pretty typical for inductors using switching regulators in the 100kHz frequency range.

In the photo of your inductors, from the left, I see a transformer-looking inductor, then three toroids in a group which are all yellow; one nearly covered in black, one nearly full of wire, and one empty. To the right of that is an unwound plain ferrite toroid. Above the plain ferrite toroid is a nearly filled toroid which appears to be red.

So, is it the nearly filled red toroid, or the nearly filled yellow toroid that you found to be 3300uH?

I'd reduce the 3300uH inductor to around 1,000uH by removing turns.

The plain ferrite toroid, if that's what you've been experimenting with that you've called the "black" toroid - it probably has quite a high AL value. You could try using it if you'd like. You should wrap it with a layer of tape (masking tape would be OK) as this will delay the onset of saturation. If your toroid saturates, your MOSFET will get hot very quickly.

 

Thank you for your reply.

sorry about the lack of clarity. In the image you can see a bare yellow toroid , about half a centimetre to its right is the black toroid I was referring to and if you look strait up in the image you will see the 3k3uH inductor I mentioned.

I had quite a bit of trouble working out the values to put into the calculator, not to mention how to use it. It is all sorted now though.

I found an old computer power supply and luckily found a 300uH inductor with 0.7-0.8mm enamel wire which should be more than enough for 6 amps. I have finished both inductors now and they both read the exact values I need.

All the parts have arrived and I am now drawing a schematic out to decide their best placement on the stripboard. One thing I would like to confirm is exactly how to connect the P channel mosfet. I have found the information on the data sheet about which pin does what but I am not sure how it fits of the schematic and googling has not helped much. Logically to me: gate would run from pin 3 on the 555(after going through R4 and C3), source would connect to D1 and L1 and drain would connect to the battery positive terminal. Or source and drain being reversed if the names refer to conventional flow of electricity. Can someone solidly confirm how they should be connected?

Yea, it will be a good idea to check the temperature of all parts every few minutes after I first hook it up to make sure everything is up and running smoothly.

 

I found an old computer power supply and luckily found a 300uH inductor with 0.7-0.8mm enamel wire which should be more than enough for 6 amps. I have finished both inductors now and they both read the exact values I need.

OK, good.

All the parts have arrived and I am now drawing a schematic out to decide their best placement on the stripboard.

You already had the schematic. What you're doing now is the board layout.

One thing I would like to confirm is exactly how to connect the P channel mosfet. I have found the information on the data sheet about which pin does what but I am not sure how it fits of the schematic and googling has not helped much.

Perhaps you missed the letters "g", "d" and "s" by the MOSFET terminals in the schematic on the previous page.

Logically to me: gate would run from pin 3 on the 555(after going through R4 and C3),[/QUOTE]

Yes.

source would connect to D1 and L1

No. Look at the schematic for the MOSFET pin labeled "s".

and drain would connect to the battery positive terminal.

No. Look at the schematic for the MOSFET pin labeled "d".

Or source and drain being reversed if the names refer to conventional flow of electricity. Can someone solidly confirm how they should be connected?

With P-ch MOSFETs, the source terminal is almost always connected to the most positive part of the circuit. When Vgs is less than the threshold voltage, the MOSFET is considered OFF. When Vgs ~=-10v, the MOSFET is considered fully ON.

 

I see that the P channel mosfet has s,8 and d marked on it, which helps a bit.

I remember that it was advised to connect my float charger (has not been built yet) with the positive terminal to the battery positive terminal and the negative terminal between L1 and L2. While researching electronics I have discovered that much of my former knowledge about electronics is incorrect or is lacking in context making things confusing. I used to think that to recharge a battery you connect the positive from the charger to the negative battery terminal creating a circular circuit. This is incorrect isn't it? If so it is blurring the line between capacitors and batteries.

Would to be worthwhile putting a bypass capacitor in parallel with C4?

 

I see that the P channel mosfet has s,8 and d marked on it, which helps a bit.

That is not an 8; it is a lowercase g.

I remember that it was advised to connect my float charger (has not been built yet) with the positive terminal to the battery positive terminal and the negative terminal between L1 and L2.

That is basically correct. If you connect it across C4 with the positive lead on top, that is the same thing.

While researching electronics I have discovered that much of my former knowledge about electronics is incorrect or is lacking in context making things confusing. I used to think that to recharge a battery you connect the positive from the charger to the negative battery terminal creating a circular circuit. This is incorrect isn't it?

That is incorrect, and would result in lots of smoke.

If so it is blurring the line between capacitors and batteries.

They are sort of vaguely related.

Would to be worthwhile putting a bypass capacitor in parallel with C4?

You can add caps in parallel with C4. I added several.

 

I have spent the last few hours soldering some of the components in place. I am having quite a bit of trouble keeping the components in place for soldering. I will need to work on that.

It does look a bit like an older style of writing out a G now that I look at it more closely.

What capacitors did you add in parallel with C4 and what advantages did they give your design?

 

I have spent the last few hours soldering some of the components in place. I am having quite a bit of trouble keeping the components in place for soldering. I will need to work on that.

It's not hard. Insert the leads in the holes, and bend at least two of them opposite ways. You don't have to bend them flat against the board, either. Solder the leads, and then clip them off.

It does look a bit like an older style of writing out a G now that I look at it more closely.

It's similar to the font "New Century Schoolbook". They really should have used a sans serif font, but that's neither here nor there.

What capacitors did you add in parallel with C4 and what advantages did they give your design?

I added several 100uF caps in parallel. This reduces the effective ESR (equivalent series resistance) of the combined capacitors vs simply using a single larger cap or more expensive low-ESR caps.

 

The desulfator is done. At long last!

I just want to thoroughly go over it to make sure there are no solder bridges and everything is hooked up correctly then I will test it. Hopefully the charger will be finished tomorrow.

So in this design the amount of capacitance is of little importance as long as it is above 100uF? I have extra capacitors so if it does overheat I can simply add more.

They should have made the font clearer, slight ambiguity can cause a lot of trouble.

One of the inductors is a bit loose, is it standard epoxy that is used to hold components in place? I am unsure if it would eat or damage them.

Lets hope all goes well and that I have not mistakenly made a doomsday device.

 

I have a problem. I meticulously went over the whole thing and fixed the only problem I could find, a missing wire coming out of pin 8 of the 555, and chose to plug it in. The moment I connected it I saw a flash from the fuse. I am very glad I chose to add a fuse to the design. Turned out that in my eagerness to protect the 555 from damage I forgot to actually put it in the DIL. I slotted in the 555, replaced the fuse and thought that the problem was solves. Nope, I connect it up and instantly, the fuse blows.I can not see any solder bridges, could I have missed one or has one of the components been damaged by the lack of the 555 or something else?

I will come back to this in the morning with a fresh head.

Thank you

 

Just thought I would give an update.

This morning I noticed that I forgot to remove part of the strip board, resulting in the two battery terminals being directly connected.

I connected it for a few minutes and all seems well. No capacitors exploded and no signs of overheating, just a slight hum coming from the device. I will check again in an hour and then reconnect the batteries to the old battery charger to monitor how long it takes them to charge.

Thank you