24 volt cap pulser battery swapper

[Sephiroth]

Thanks Ren!

I have a 555 circuit triggering a relay exactly as I want it to now... split second on time with variable off time.

Though can't get the scr circuit to work now! I think the problem is the SCR I am using... it looks like the raw output of my device is high enough to keep the SCR on so it doesn't turn off to charge the cap.

Oh well... the relay seems to work anyway!

[ren]

hmm. Perhaps your scr is damaged. What part number is it?

[Sephiroth]

lol... I damaged about 6 of them! By damaged i mean blew up in a puff of smoke. they are not suited for the job but are the only scrs I can get (unless I buy them online.)

Part number : CP106D

Need bigger ones. I know the last one I tried was still working because I tested it manually afterwards.

[ren]

hmmm. Couldnt find any specs online for it. Gotta love the little puffs of smoke.

I only have one 800v 16 amp scr available here without going online for some. I can post ya a few if you want, they are about $4 each

[Sephiroth]

Thanks Ren, that's very generous of you to offer, though I will get some online eventually I like to buy a load of componants at once to save on the postage. (I'm a cheapskate!)

Though I'm very happy with how the relay is performing at the moment so I'll do some load tests with this method before trying the SCR.

Thanks again!

[ren]

No worries mate, if you want some let me know, they have worked well for me.

Lol at the bulk buy. I went into the local shop the other day and brought $10 worth of 1n914 diodes. Only wanted one, but just got sick of never having one!

Ill never run out now!!!

How does the relay go at charging?

[Sephiroth]

pretty good though still doing load tests... I have it set to charge a 1000uf cap up to 50v then it discharges down to 25v every second when charging a 12v battery.

[ren]

A good tip I learned from John K on the monopole forums was to use an analogue meter to read the potential of the voltage dump. I have a analogue gauge good for 10/50/250 volts. Gives you a good idea of whats going on.

On a side note I switched on my solid state device the other day without a load to see how high the voltage went in the cap. The cap is only small, its 33uF 250 v but it shot up to over 300 volts almost instantaneously off 24v input. Gave me a little scare

[mlindeblom]

I am doing a series of tests on various capacitor sizes and various timings.

To simplify the timing I used a Atmel Attiny13 micro ($1.51 at Digikey). It allows virtually any timing ratio. I have used 30 msecs on, 70 msec off thru 120 msec on and 190 msec off.

I have used from 470 uF thru 40,000 uF.

I am having difficulty in determining the optimum arrangement of capacitors and timings.

Yes you blow parts if you allow the discharge current to get too high.

I am using PS2532 opto couplers and S8055 SCR's.

Many people seem to recommend large capacitors and about 2 volts above the charge battery voltage.

Does anybody have some experience to guide which dirrection gives the best COP's, etc other than the usual answer of it depends?

[ashtweth]

Great Vid Ren, thanks for this. Really gives me confidence on the Relay on the Fan kit we have, ill be teting that soon, got 3 bats conditioned for it, i think the fan kit is a cap pulser, Be nice if you had a load on that shaft, i bet you could some where.

Ash

[ren]

Thanks Ash, yeah the shaft could do with a load, but I was primarily interested in the capacitive discharge. Look forward to seeing your fan replication


By the way Ash, where are you located?

@mlindeblom. I can only speak from what I have tested and I have found the larger uF caps performed better in my experiments with my batteries. It did depend though, I used a really small cap, 33uF 250v on a solid state number that works well too, especially on smaller batteries. Im sorry I cant offer you much more than that.

[mlindeblom]

Thanks for the reply.

It appears the question is more complex than it appears on the surface.

I highly recommend using a micro instead of a 555. I changed timing from 30 msec on and 170 msec off to 30 msec on and 2470 msec off in less than 5 minutes.

I think the reason many people blow SCR's is they under estimate the surge currents involved. The lower voltage ranges 2 to 5 volts above charge battery are much safer to start with. Measure the voltage across the SCR. The effective resistance of an SCR is in the low milli ohm range.

[ashtweth]

Thanks Ash, yeah the shaft could do with a load, but I was primarily interested in the capacitive discharge. Look forward to seeing your fan replication


By the way Ash, where are you located?

@mlindeblom. I can only speak from what I have tested and I have found the larger uF caps performed better in my experiments with my batteries. It did depend though, I used a really small cap, 33uF 250v on a solid state number that works well too, especially on smaller batteries. Im sorry I cant offer you much more than that.

Hi Ren sorry mate i missed this one. Am in Brisy mate, we are just about to goto the truckers strike on Monday with boosters and web site, they will also be reading your window motor Doc too

[ren]

Cool mate! Sounds good. If your ever down Sydney way (central Coast) gimmie a yell

[selamatg]

Hey Sep, I think your right, the transistor/scr arrangement amplifies the signal much like a darlington pair would. The H11d1 opto isolator is there so there is no direct link to the 555, thus protecting it. You may notice some similarities to the 555 circuitry on this page here:

http://tacashi.tripod.com/elctrncs/555sstc/555sstc.htm

Ok, to start with, I have attached a drawing of Johns schematic with a couple of extras which arent necessary, but can help beginners such as myself. If moderators find this a breach of copyright then please remove with my apologies, I know of two places on the net where this schematic is posted in full so I saw no problem with it. Once again, it is Johns schematic not mine, I have only added a couple of things.

Get yourself a little PCB prototype board, preferably like the one in the picture below. It spaces out the pins and makes soldering and joining them SO much easier! Remember each pin on the 555 and the opto must be isolated from each other, important to note if you can only get a PCB prototype board with rows and not separate pin holes!

Also, in the interest of simplicity get a 555 cradle and a 6 pin optoisolator cradle (machined pins if possible) this will save you soldering directly to the components themselves, most likely destroying them if you arent careful. This way you can swap them in and out if you damage them too. Take note of the pin references of each component carefully, especially the opto isolator. There are heaps of places on the net if you want diagrams for specific components.

Pins 8 and 4 on the 555 are joined together, so are 2 and 6. I put an extra cap between 8 & 4 (+) and 1 (-) to smooth out the voltage going to the 555. I was told JB said this is a good idea. 10 uF cap should do fine. The 1 uF cap is specified at 600volts I think but mine worked with a 63 volt 1uF cap. Resistor between 8/4 and 7 and second resistor between 7 and 2/6. I found you could vary the dump speed by varying this resistor. Maybe use a 10k and a 150k pot. Pin 3 is the output and it loops through the H11d1 before returning to ground through another resistor. I put a small 12v LED between 3 and pin 1 of the opto to show the pulse frequency. It is also a good indicator of whether it is working and whether you have left it connected. It will pulse away as soon as your primary battery is connected and all switches are on, EVEN IF THE WHEEL ISNT ROTATING. Only draws about 40ma or so, but it will flatten the battery if left connected.

Pin 3 and pin 6 on the opto arent used. Take note of the way you install the cradle and make sure your opto goes in the right way, same goes for the 555. There is a little notch cut out of both which signifies the top. 1 and 2 on the opto are pretty self explanatory, same with 4 and 5. 5 goes directly to the negative of the charge battery, or to make things easier, just connect it to the anode of the SCR. The Collector of the transistor is also connected to the SCR's anode. The cathode of the SCR goes to the negative terminal of the cap.

For the triggering transistor I couldnt find the one specified so I just tried to match basic charateristics. The 2n3440 or the MJE340 have both worked for me, they are both 300v rated. You may even find a 2n3055 will work ok, if you use a larger capacitor, say in the 1000's of uF's. I believe Aaron has used others here successfully too.The collector of your transistor connects to the anode and the emitter connects to the SCR's gate. The base of the transistor is triggered by the opto, pin 4. It makes sense when you trace the lines on the diagram. Please note if you use the MJE 340 the pins are reversed. What ever transistor you use, google it for a spec sheet to make sure you got everything right.

Take your time, especially with the 555 and opto. The pins can be a little trickey but if you have a cradle for them both you can afford to be a little reckless when soldering Just make sure there are no shorts between the pins.

And as always, I must state that I am no pro, and if anyone else has info or deems some of the above unecessary or incorrect please dont hesitate to post. Enjoy


PS oh and by the way, the 555 is limited to 18 volts input, so if you want to run your front end higher than that then it needs a separate source. For the 24 volt cap pulser I posted above I used a 3 pin voltage regulator to automatically drop input voltage to 12 volts. The voltage regulator is good for 35 volts on the front I think, with a 1 amp output max. Thats heaps as the 555 only needs 40 ma or so.

Hi Ren,

I have try built the timer as your explaination above.
and I put a small 12v LED between 3 and pin 1 of the opto to see the pulse frequency too.. the circuit is work without OPTO connected (the LED on and off) but when I put the OPTO on.. the LED is goes off.
this happen even I only connect pin 1 and 2 of the OPTO.

I have try with 5 opto with same result.

Please anyone can assist me on this problem.

Thank and regards,

Selamatg