Author Topic: The Spark-O-Matic - Wire Arc Welding for coil making (Read 493433 times)

Breaktru · « **Reply #551 on:** August 28, 2015, 08:15:28 AM »

Yes that is the same brand meter I used. I used the PMLCDL model
You will need to use a separate 9V battery to power the meter.

beefy0678 · « **Reply #552 on:** August 28, 2015, 08:25:57 AM »

Excellent, to start with all i could find was ones from america which would of cost loads in imort duties and postage lol

Which resistors did you use with your panel for the voltage output or are they on one of the schematics on here?

Breaktru · « **Reply #553 on:** August 28, 2015, 09:08:17 AM »

A 9.99M and a 10K resistor as shown HERE

Also see attached below (omit the ohm reading portion) -

beefy0678 · « **Reply #554 on:** August 28, 2015, 11:51:54 AM »

Quote from: Breaktru on August 28, 2015, 09:08:17 AM

A 9.99M and a 10K resistor as shown HERE

Also see attached below (omit the ohm reading portion) -

You're a star!

I was thinking about the charging light and how it gets brighter the more charge goes into the capacitors to let you know when the flash was ready and wondered if there was an easier way to measure the voltage through that... but then i realised that i don't know squat compared to you guys and if that had been an option then you would of thought about it lol

Thanks for the quick replies and the great information. Much appreciated as always!

MildBill · « **Reply #555 on:** August 30, 2015, 03:33:39 PM »

Just a quick "Hello!" and a (hopefully) quick question from a new member...

Hello!

(

)

I see that in the last couple of years the majority of welders seem to be in the lower voltage category (30 - 42 range), with some fairly reliable success even with silver wires at around 32 volts. I'm guessing that higher capacity capacitors (in the range of 1900 to 2200 microfarads ?) are being used. Anyone have any actual factual information on any of these lower voltage devices, and what capacitances they seem to be using?

MildBill

Breaktru · « **Reply #556 on:** August 30, 2015, 06:48:01 PM »

I believe you are referring to the LM board welders:

http://breaktru.com/smf/index.php/topic,727.0.html

http://breaktru.com/smf/index.php/topic,952.0.html

MildBill · « **Reply #557 on:** August 31, 2015, 10:52:51 AM »

Quote from: Breaktru on August 30, 2015, 06:48:01 PM

I believe you are referring to the LM board welders:

Well, not necessarily the LM board, but thanks, I'll give these a look.

MildBill

P.S. I do like better the notion that, once I find my 'sweet spot', I can more or less set it and forget it and churn out a small batch of wires at a time.

MB

beefy0678 · « **Reply #558 on:** August 31, 2015, 03:36:24 PM »

I found these caps today in one of my old computer power supply, i was stripping one down to use the case for this project.. (I am not a vain man and don't caree what it looks like as long as it works lol)

the one on the top is the one i found, 330uf @200V, underneath is the fuji board.

Would it be ok to use this cap on it's own?

I know it would take longer to charge but could i run 2 AA batteries in parallel to help with the charging?

One more thing for Breakthru, in the schematic you have put up with the panel reader, on the right hand side you say don't not remove the RA resistor that is in situ, but remove the one in RB, so i take it that i solder the new resistor (10k) over the top of the little resistor in RA, then remove the resiistor in RB and solder in the 9.99Mohm resistor into there instead, remember i am only going for the voltage meter, not the ammeter yet. That will give me the 200v reader that i want?

Thanks In Advance!

Breaktru · « **Reply #559 on:** August 31, 2015, 04:48:50 PM »

beefy, I don't know if you intended to place a picture in your post or not but I don't see it.

330uF is fine as long as you keep your output voltage well below 200V. Otherwise it will definitely POP. Use w/ caution. The camera flash caps are rated at 330V. You should be safe if you don't accidentally overcharge the cap.
There is no need for parallel batts but it will extend the life of usage.

Leave the existing smd resistor on RA and solder across it w/ a 10K ohm resistor. The resistor should be a low tolerance rating of 1%, preferably lower. And yes it will be the 200V setting.

beefy0678 · « **Reply #560 on:** August 31, 2015, 04:58:27 PM »

There you go i put the picture in, god knows what i linked to...

MildBill · « **Reply #561 on:** September 01, 2015, 04:07:43 PM »

I'm still doing some research, but it occurs to me that the switches in the original project that started this may have been changing out different Zener diode voltage regulator circuits, which should be fairly simple to add to this version, thus negating the need for a voltage meter permanently installed. It would also allow, once the specific voltages were determined for the various sizes of wire, that 'set and forget' notion I seem to have. You could easily have 5 different voltage levels, (one for each switch, plus one 'maximum' voltage for the whole thing) with the type of switch in that original project.

Select your voltage, press the charge button, wait a few few seconds for the voltage to stabilize, and ZAP!

Just a passing thought as I did my research.

MildBill

beefy0678 · « **Reply #562 on:** September 02, 2015, 04:14:55 PM »

Quote from: MildBill on September 01, 2015, 04:07:43 PM

I'm still doing some research, but it occurs to me that the switches in the original project that started this may have been changing out different Zener diode voltage regulator circuits, which should be fairly simple to add to this version, thus negating the need for a voltage meter permanently installed. It would also allow, once the specific voltages were determined for the various sizes of wire, that 'set and forget' notion I seem to have. You could easily have 5 different voltage levels, (one for each switch, plus one 'maximum' voltage for the whole thing) with the type of switch in that original project.

Select your voltage, press the charge button, wait a few few seconds for the voltage to stabilize, and ZAP!

Just a passing thought as I did my research.

MildBill

I was wondering about the charging LED. It gets brighter as the voltage goes up so could you mount a set of different coloured LEDS and add resistors or something so that they light up when you reach a certain voltage?

There must be loads of ways to do this and i think we have only just scratched the surface.

beefy0678 · « **Reply #563 on:** September 03, 2015, 01:24:11 PM »

Quote from: MildBill on September 01, 2015, 04:07:43 PM

I'm still doing some research, but it occurs to me that the switches in the original project that started this may have been changing out different Zener diode voltage regulator circuits, which should be fairly simple to add to this version, thus negating the need for a voltage meter permanently installed. It would also allow, once the specific voltages were determined for the various sizes of wire, that 'set and forget' notion I seem to have. You could easily have 5 different voltage levels, (one for each switch, plus one 'maximum' voltage for the whole thing) with the type of switch in that original project.

Select your voltage, press the charge button, wait a few few seconds for the voltage to stabilize, and ZAP!

Just a passing thought as I did my research.

MildBill

I really like your idea, we need someone to let us know what the voltages are for the different size wires and thats it we will be well away, plus we also need someone who can draw diagrams lol just had a look, they have 75watt zener diodes and everything up to 200 volts so we should be ok with this.

I am stilll making the one with the voltmeter panel, I am making it in an old PC power supply box, once it is done i will put it in a small plastic box and tidy it up. But the more i think about it i think your idea is great, just hold the button down for a while then zap, you shouldn't get any voltage drop either as you aren't trying to measure it.

Nice idea, thanks for sharing!!

MildBill · « **Reply #564 on:** September 03, 2015, 06:26:06 PM »

Quote from: beefy0678 on September 03, 2015, 01:24:11 PM

I really like your idea, we need someone to let us know what the voltages are for the different size wires and thats it we will be well away, plus we also need someone who can draw diagrams lol just had a look, they have 75watt zener diodes and everything up to 200 volts so we should be ok with this.

Not sure it will be quite that easy, as the voltage will change with the specific value for the capacitor(s) used, but it would be a good place to start at least. Do note that some of those zener diodes can be quite pricey, so bringing the voltage down a bit to go with more capacitance may be part of the overall plan. I am also curious, for anyone out there who has perhaps tried more than one type, if the lower voltage/higher capacitance versus higher voltage/lower capacitance makes a difference in the weld quality.

Quote

I am stilll making the one with the voltmeter panel, I am making it in an old PC power supply box, once it is done i will put it in a small plastic box and tidy it up. But the more i think about it i think your idea is great, just hold the button down for a while then zap, you shouldn't get any voltage drop either as you aren't trying to measure it.

Hope it works out for you, do please keep us posted.

Quote

Nice idea, thanks for sharing!!

No probem, as I say, I'm still doing my research on the idea.

MildBill

beefy0678 · « **Reply #565 on:** September 04, 2015, 08:37:15 AM »

Well i have just rang up the supplier for the panel meter and the precision resistors as i didn't recieve an email off them, i only ordered them on the 1st and they should be with me by tomorrow or monday! I will let you all know how much they charged me in the end as like i said the haven't sent me an invoice, plus i ordered 2 packs of resistors just in case i mess one up and they only had one in stock, but they are getting more in monday so they have sent it out in 2 packages which i think is awesome!

All the rest of the parts should arrive shortly and i can get to work making this beauty!

I am starting off with it in an old emptied out PC powers supply and when i get it all working i will move it all to a nice plastic box

*edit - the Velleman panel meter and the one pack of resistors arrived today just as i was writing this. The price is £11.75 for the panel meter and 2 packs of the resistors from here : https://www.esr.co.uk/electronics/test-panel.htm

It will be about a pound cheaper if you only get one pack of resistors but i am still prcticing with my soldering lol

At the end of all this i think it will have cost me about 25 - 30 quid, but i will have the Pleasure of making it myself and it won't be one of the ones where you have to hold the button down for an undisclosed amount of time and hope that if works for £40

Big Kudos to Breaktru and his team for helping out the newbies and doing such great work!

Thanks from us all!

beefy0678 · « **Reply #566 on:** September 05, 2015, 09:48:22 AM »

This might sound like a really dumb question, but i take it that i disconnect the flash right?

Yes, take the piss if you want but nowhere doesw it say to disconnect the flash...

Breaktru · « **Reply #567 on:** September 05, 2015, 10:19:04 AM »

Yes beefy. Cut out the flash

beefy0678 · « **Reply #568 on:** September 05, 2015, 10:23:25 AM »

Quote from: Breaktru on September 05, 2015, 10:19:04 AM

Yes beefy. Cut out the flash

Sound, i know it sounded stupid but i just thought i would ask. Nearly got everything to make it now, should have everything by next week! Can't wait lol

beefy0678 · « **Reply #569 on:** September 12, 2015, 07:32:01 AM »

And here comes another dumb question...

I have been trying to read the resistors resistances with no luck, i have even tried using an online calculator but they don't seem to correspond to the colours on the resistors no matter which way round i do it, some do, others don't. can you please just tell me which colours you used for the panel meter please?J ust for the voltage, i don't care about the resistance meter at the moment.

I calculated the 15k resistors for the bleed button easily and have tried different ones i have got on other things i have stripped down, but i just can't seem to figure out these blue bloody precicion ones!!! AAAArgh!!!

As always your help with my stupidity will be very grateful!

Breaktru · « **Reply #570 on:** September 12, 2015, 09:14:32 AM »

Attached below is a color code chart for 4, 5 or 6 band resistors.
A 10K would be: Brown, Black, Black, Red and the Green band would signify 0.5% tolerence

beefy0678 · « **Reply #571 on:** September 12, 2015, 10:29:08 AM »

Thanks mate,

It's just bit hard to make out some of the colours on these bloody things, i think i might be going colour blind lol

Thanks greatly!

MildBill · « **Reply #572 on:** September 12, 2015, 04:14:48 PM »

Quote from: beefy0678 on September 12, 2015, 10:29:08 AM

It's just bit hard to make out some of the colours on these bloody things, i think i might be going colour blind lol

Yeah, that's the real problem in many cases, deciding on what color the band(s) really is, especially on older resistors I've 'recovered' out of some other project/board.

MildBill

waverunr2001 · « **Reply #573 on:** September 17, 2015, 09:03:07 PM »

Hi All,
You know with all the devices out today reading two digits past the decimal point, even cheap ohm readers. You'd think we could find a way to do it too. Has anyone figured out how to get two digits past the decimal point yet? I even saw a ohm reader that goes three digits past! I'd really like to add that to my welder. The meters on them dont look anything special either. Any suggestions?

MildBill · « **Reply #574 on:** September 17, 2015, 09:25:30 PM »

I suppose we could find the ohm meter module that they all seem to use... I have seen one on a UK vape shop site, but I can't seem to find it at the moment, and I saw one once on a site with electronic modules, but again, have been unable to find it again. The one I remember was apparently made by MMT, a Chinese outfit, as that was the label across the board.
The vast majority of cheap readers out there seem to use this module, glued or potted into a 3 'AA' cell battery box, thus taking up one of the battery slots along with the 510 connectors, including the (original model) ones 'Made proudly in the USA'!
What I keep hoping to find, somewhere, is the board used in the Coil Master 521 Tab, but I'm not holding my breath.
But, to be honest, I have pretty much decided, for myself at least, that an ohm meter in the same box as my welder is overkill. I'd rather have my ohm meter separate. I'll probably end up buying that Coil Master build deck.

MildBill

EDIT: Here's the board in question on AliBaba, maybe someone would do a group buy?? http://www.alibaba.com/product-detail/MMT-Group-original-developed-pcb-digital_60159889494.html

Breaktru · « **Reply #575 on:** September 17, 2015, 09:43:49 PM »

I gave up trying to get it to read hundredths or thousandths. This is what happened when I tried w/ the PMCDL meter: SEE THIS POST

Duckster · « **Reply #576 on:** January 22, 2016, 07:32:17 PM »

I just spent an extremely long informative post to respond to "ILoveToBuild", but I took too long, and it logged me out, and I work Midnights so no chance to redo.

Breaktru · « **Reply #577 on:** January 22, 2016, 07:47:29 PM »

Wow, sorry about that Duckster. Didn't even know there was a time limit.

Duckster · « **Reply #578 on:** January 22, 2016, 08:24:58 PM »

Deleted by Duckster accidental duplicate.

Duckster · « **Reply #579 on:** January 22, 2016, 08:26:25 PM »

To " ILoveToBuild" the Reader Digest Condensed version to my lost post is.
I believe that the circuit using the LM317 isn't a voltage idea, but a Constant Current Source, standard way to measure resistance, is to apply a known current through a unknown resistance, and measure the Voltage Drop to represent the resistance. If you provide a 100ma signal, and using the 200mv scale, at .75 ohms the drop would be .075V or 75mv. Depending on the digits the display has available, you can read up to 2ohms, or 200mv with the corresponding resolution. Also a LM334 would be a more stable and accurate source for the current, and this is what I will be using. Correction my bad, this is only the case if using it for a source up to 10ma. Up to 1 amp use the Lm317.
I also hit on the idea that the exposed lengths both being kept short due to the higher resistance of Kanthal to Nickel, when I tried this in my first attempts at work with trouble during my free time,

maybe the lengths should be varied so the higher resistance Kanthal would not be prone to failure during welding, by adding resistance to make both wires more equal in resistance. By increasing length of "non resistance" wire or adding resistance to the wire on that side? Resistance higher typical 1.2-1.8 coil can use the lower power mod, but Sub ohming requires more power, so when the weld happens with them both set to short lengths the higher resistance wire heats up usually too quick causing failure.
Bought 10 photo flash circuit boards from All Electronics for .85 each but shipping $8, Ouch!! Delivered in 3 days, just started playing with them today, didn' t add Extra Capacitance yet, tried 60-75 Volts and above, not real good results.
Seen post yesterday for this circuit by "Breaktru" , real similar to the way I was already leaning, but I haven't, made anything yet, except in my head.
Fasttech has a Display I believe with similar capabilities. Good job as always for Breaktru

I also noticed someone using what appeared to be a microprocessor for Display and Control, aka "Arduino" very interesting. Components are inexpensive if you buy the knockoffs, with great possibilities, the negative is that it will take a learning curve to learn how to do the programming.

I hit on how we made circuit to weld Platinum/(Plat-Rhodium) wire together to make precision welds for thermocouples, for possible interest of knowledge. Questioned if a welder could be made more similar to how a spot welder work?

I will try to repost again for this. Instrument Repair by trade.

Duckster · « **Reply #580 on:** January 23, 2016, 04:29:55 PM »

Here is a link which someone referred to which I find helpful to help understanding about rescaling. http://www.eidusa.com/Electronics_DPVM.htm

Duckster · « **Reply #581 on:** January 23, 2016, 04:35:15 PM »

Here is a link which someone referred to which I find helpful to help understanding about rescaling. http://www.eidusa.com/Electronics_DPVM.htm

beefy0678 · « **Reply #582 on:** January 30, 2016, 01:07:01 PM »

Breaktru,

I am finally getting enough free time to have a go at doing this but i can't find all of the schematics, is there any chance that you can post all of the ones you have done so far? I know i am asking a lot but i have searched and can't seem to find the one i am looking for!

Thanks in advance!

Breaktru · « **Reply #583 on:** January 30, 2016, 02:10:02 PM »

beefy, if you look at the first (OP) post you will see a link to"Wire Schematic/Diagram". That schematic post will have a link to the next schematic. Each posted schematic has a link to the next schematic.

beefy0678 · « **Reply #584 on:** January 30, 2016, 02:32:37 PM »

Doing that only gets me 3 different schematics. I need the one with just the PMLCDL meter being used as a voltmeter and nothing else but i can't find it. all i can seem to find is the ones before or the one after with all the resistance metering.

It's making my eyes hurt going through all this.

I knew i shouldn't of upgraded my pc...

Breaktru · « **Reply #585 on:** January 30, 2016, 03:42:04 PM »

Sorry,
It was the last link in the OP: With Volt and Ohm Meter

Duckster · « **Reply #586 on:** January 31, 2016, 05:28:17 PM »

Hi Breaktru still planning stage.

I was reviewing your circuit diagram again and at first I couldn't see the simplicity of you not removing the existing smd resistor Ra and replacing with the values needed to get different scaling for ohm meter versus voltmeter, but electrically it would be the same as if you put the resistor across the voltage input terminals , AS NORMALLY DONE EXTERNALLY FOR THE DIVIDER NETWORK. This added resistor is for the attenuation of a higher voltage input down to the original 200mv level of the meter, so you are in parallel with the internal op amp input. When compared to the more in depth information for the Murata DMS-20LCD voltmeter from Digikey, they internally don't even use a resistor in parallel with their op amp input on the 200mv and 2v models. This model I assume is only available in a standard 200mv range. Assume Rb is a jumper as noted in literature, therefore electrically I should be able to leave jumper in and just put this resistor in series with the positive input instead if desired, right?

Likewise you using only one 9.99M ohm resistor for Rb instead of 2 different Rb values (90K difference) as calculated or shown in the user manual for 20v (Equating to 20 ohm F.S.) and 200v scaling. Is this because the change in total resistance and therefore current through the Ra used to create a voltage drop to be measured at the meters inputs is negligible for the ohm meter. Especially since you are not taking resistance measurements out to maximum decimal places available, and possibly compensated if necessary by adjusting the Lm317 output. A theoretical 198.222mv vs ideal 200.000mv drop at input at full scale resistance, and the resistors are what .5% tolerance anyways or approximately 50K ohms.
I intended in my circuit to measure 200mv range F.S.to represent 2 ohms, so no need to change original range of inputs to represent ohms of wire to be measured. I intend to just send a constant 100ma into unknown resistance and measure the Voltage Drop. Possible over voltage with higher than 2 ohm resistance but meter input should be protected in original circuit for some minor over voltage? When I try to analyze your circuit I am confusing myself, due to you using a 20volt range I believe, maybe just tired? Any help you may give on your end would be appreciated.

What decimal place is done by connecting P1 to P0, your visual shows the tenth place, but the literature states that for 200mv connect P3 to P0, and for 200v range also connect P3 to P0 which would make sense since a 3 1/2 digit meter usually is represented by for example 199.9 for ( 200v or 200mv) never reaching a 2 in the first digit?, or what decimal place is P3 to P0?

I searched everywhere and cannot find a better meter for the price than the Velleman, the Digikey's cheapest cost model (Murata DMS Series) is 3 times as much, and while it has some unique capabilities (direct ohm meter appl.) and very in depth literature it is also very confusing. For example it states that for a 9v model both "(-) INPUT LO and (+) INPUT HIGH must always be at least 1.5V above -Battery and at least 1.5V below + BATTERY.", but using it as shown for a floating point measurement (0v to F.S.) they show Analog COMM tied to (-) IN LO, but in their application notes for "Analog Common and Reference In-Out", states some older Murata DPM's must be connected to the system power supply common, is not true for new DMS Series meters. In particular never ground pin 10 (Analog Common) on any DMS-20 meter, or any of the 9V models in the DMS-30 or 40 series. States in " Input Config., P. Supplies, and Ground Loops Application Notes" 9V powered meters must never be wired in any configuration that has Inputs tied directly to or at the same potential as pin3 which is Supply Return or low or gnd. All 5V meters can be used to measure either single ended or differential inputs. In real world of DPM's many applications battery powered and also have their input referenced to or below the negative battery terminal, therefore 5V meters must be used or a 9v supply must use a 5V regulator chip. Under "Analog Common notes" Pin 1 =+Battery should always be used as the refernce point if measuring Aanalog Common not pin3=(- Battery). 9V model seems only good for mostly not practical differential inputs uses only, without changing it to 5V isolated supply.

The only other meter found which may work and has limited information available is on Ebay,http://www.ebay.com/itm/251877547606 , it has better accuracy .2% F.S., and worse input impedance =10M ohm, and only slightly more cost but Free Shipping, and slow delivery from China.
Thank you Breaktru or anyone else who can help for your patience and understanding. I am the most long winded poster out there.

beefy0678 · « **Reply #587 on:** January 31, 2016, 07:18:35 PM »

Quote from: Breaktru on January 30, 2016, 03:42:04 PM

Sorry,
It was the last link in the OP: With Volt and Ohm Meter

Thanks mate,

I don't want the resistance meter as well as i got bought a Coil Master 521 Tab for xmas so there is no point, but still have all the parts for the wire welding and want to go ahead with it, i have modified the schematic you posted to remove the resistance meter (hope you don't mind) could you check through it and see if my wiring is ok please?

Thanks again for all your help!

Duckster · « **Reply #588 on:** February 01, 2016, 08:53:24 AM »

Hi beefy0678,

This is Duckster I saw the simplified schematic from Breaktru which you posted, and yes it is set for a 200v scaling and it looks perfect, so if you wired it accordingly it should work fine.

beefy0678 · « **Reply #589 on:** February 01, 2016, 09:20:59 AM »

Quote from: Duckster on February 01, 2016, 08:53:24 AM

Hi beefy0678,

This is Duckster I saw the simplified schematic from Breaktru which you posted, and yes it is set for a 200v scaling and it looks perfect, so if you wired it accordingly it should work fine.

Cheers mate, was worried that i had missed something out, always good to have a second pair of eyes on the job ain't it!

Plus i hope that this helps some people who just want to do the wire zapper part and not the whole thing, like myself! The other one was getting a bit too complicated for me!

Thanks again!

Duckster · « **Reply #590 on:** February 01, 2016, 10:09:13 AM »

Hello Breaktru,

I had some time during my Midnight shift to think about my earlier posting and my confusion about the circuit. I am an electronics kind of guy who has forgotten a lot, but my math is usually right, and your circuit has always bothered me when I hear that you can only get it to read for the ohmmeter in the tenths place.

Please do me a favor and do a simple quick check put a known resistor say for example 15 ohms in place of where you measure your atomizer resistance, but put in series with that resistor your ammeter and let me know the Current reading, I am guessing that it will not be the 1 amp needed to develop a 20v F.S. reading, probably some factor of ten less. If it is about 100ma then when using the 20V scaling the readout would show about 1XXX = 015.0, because the voltage drop would not be 15V but 1.5V on a 20V scale, which is ultimately read as 150mv at the meter after being attenuated by your 9.99M ohm Rb and 100K ohm voltage divider.

If you wanted to read 20 ohm for F.S. if you used just no divider or default the 200mv range, the 20 ohms would show on the display as 19.99 using only a current of 10ma and the wire/coil and regulator would run cooler also. Possibly the circuit cannot generate the needed 1 Amp using a 9 volt battery for supply, you would be asking it to create a 20V drop across the measured resistor for full scale using a 9V source, sum of all drops around a loop should equal the source value or zero if it is added in. ( I believe)=Kirchoffs voltage law ( http://www.electronics-tutorials.ws/dccircuits/dcp_4.html )

I want my circuit to read to 3 decimal places, Greedy I guess, so this is why I was going to limit my Full scale to 2 ohms and use a 100ma constant current source, although I am also toying with the idea of a circuit to do also dual ranges to include 20 ohm reading using a selector for decimal point selection and an additional 10ma capability. Always trying to learn or make something better isn't this also what this forum is about, including helping each other to achieve this?

Pantera · « **Reply #591 on:** February 01, 2016, 12:55:48 PM »

I would like to point out that the ohm circuit that breaktru used is 100ma.
See: http://breaktru.com/smf/index.php/topic,733.msg8584.html#msg8584

Duckster · « **Reply #592 on:** February 02, 2016, 09:42:41 AM »

Well if the circuit that Breaktru used is indeed set at 100ma then, yes this is why he can only read to the tenth place using a 20V scaling, as I explained in my post. If anyone wants to read to more places after the decimal point then they need to change the scaling, which wouldn't take much of a change in the existing circuit.

Duckster · « **Reply #593 on:** February 02, 2016, 10:39:15 AM »

Pantera,
Thank You for the link, I never saw this before, it would of saved me a lot of grief, it verifies what I said in my very first post trying to respond to " ILoveToBuild" who posted this « Reply #526 on: January 09, 2015, 02:21:39 AM , When I try to do a simple copy and paste it ends up the wrong location in thread. I am new to posting I can't even seem to copy the link for ILoveToBuild. Can you give any guidance on this or even using the "quote option"?

Duckster · « **Reply #594 on:** February 02, 2016, 10:57:28 AM »

Patera and this is the subsequent reply by Breaktru to ILoveToBuild

Quote from: Breaktru on January 09, 2015, 04:20:08 PM

The best we can do with this meter is read tenths. I have previously wired in a switch with P3 to P0 for ohms reading and what happens is an ohm reading like 01.5 will show as .015 You don't actually see the hundredths number. It just moves the decimal point.

I prefer the 200 ohm pot over the 500 ohm. It's better for a finer adjustment.

You won't see any difference with a 15K over the 10K for the discharge.

You won't be able to illuminate an LED as an On/Off indicator with a 1.5V AA battery. On my original Spark-O-Matic, I built a Joule Thief circuit as shown HERE

Breaktru · « **Reply #595 on:** February 02, 2016, 11:55:02 AM »

Yes Duckster, I had wired in a switch. One position used the 200V scale for welding (P1 to P0) and another position of the switch for the 200mV scale (P3 to P0). Like I said previously, it only moved the decimal point.

Duckster · « **Reply #596 on:** February 02, 2016, 12:23:38 PM »

The link that Pantera shows is originally posted by you, and it correctly shows exactly what I originally intended for my circuit, since most builds of mine are not higher than 2 ohms. It should yield 3 places after the decimal point and only 2 ohm maximum measure. Your later circuits where you are getting only one decimal place, your choice of voltage divider resistors implies you are going for a scaling of not 200mv but 20V, which would put the decimal point to 10ths.

Duckster · « **Reply #597 on:** February 02, 2016, 12:27:00 PM »

I am bouncing back and forth from your Forum and Ebay trying to find an appropriate plastic box. What size did you end up with, hate being from U.S. having to convert from metric measure when looking.

Breaktru · « **Reply #598 on:** February 02, 2016, 01:14:10 PM »

The boxes can be found in the OP under "More Parts". Here's the link: http://breaktru.com/smf/index.php/topic,733.msg8251.html#msg8251

Duckster · « **Reply #599 on:** February 02, 2016, 02:24:49 PM »

Upon reading some of the recent post, some are confused as the purpose of the P0=common, P1,P2,P3 these have absolutely nothing to do with the meter scaling, they only move the decimal point to reflect the correct range. A raw maximum reading =1999 which can represent 199.9V or 19.99V or 1.999V if there was a 2V range, or 199.9mV. You choose the Range desired, then set the decimal point appropriately. Just as 199.9 can represent 200V scaling or 200mV scaling as noted in Velleman User manual, and is why you will see both those scales using P0 to P3. I don't know why they are not clear about P0 to P1. The 500V based on choice of their resistors would use no decimal point. Maximum drop when 500V applied would be .05V or 50mV seen by the meter.

In all cases other than the base 200mv range the total divider resistance will always be the sum of the 2 resistors( Ra + Rb) or always 10M total. Knowing this and using ohms law E/R=I, you'll find the current going through these resistors, once you know the current, you would then multiply it by the smaller voltage dropping resistor. E=I times R The input is wired across this resistor, same as the ohm meter application.

!) 20V range meter would see E/R=20/10M=.000002Amps then this times Ra (100k)=.2V=200mV seen by meter
2) 200V range meter would see E/R=200/10M=.00002Amps then this time Ra(10k)=.2V=200mV seen by meter

This is why it is scaling because you are dividing it down or attenuating the high Voltage down to the level which the meter is designed to see for Full Scale, it can NEVER be anything else for Maximum but it can be less as in the case of the 500V range. The 10M total resistance is what the manufacturer deems as the ideal resistance to use, which is Designed or dictated by/for the lowest scale or input which uses no External resistors to achieve the 200mV range.

Hope this isn't too confusing, I need to make picures and drawings to help explain, but I am new to this posting, not sure best way, Paint, Works or what program to use.