Model Engine Ignitions

[Lagerbolzen]

All very interesting life experiences chaps, but could we perhaps keep loosely on the model ignition theme.

 

[Steamchick]

Ooooops!
(Sorry).
K2

 

[74Sprint]

Well Ray, Sorry to hear of your shocking experience!
I hope my explanation of the ignition is somewhere close to what is really happening... it is a compilation of all my varied experiences of "sparks" - and deducing what is happening...
Curiously, when lightening strikes, the thunder is the sound of the shock wave of the rapid collapse of the fine thread of expanded gas from the arc. And - please correct me if I am wrong? - a plasma is created in every arc where the current flows in the ions? (even in the corona from HV electrical kit). - The ions make-up the plasma (I think?). The temperature of the plasma is easy to see as it is white~blueish... 2000 ~5000 deg.C? I.E. the "visible spark" of light emitted from the electrons leaping to higher energy levels from electrical energy input, then falling back to their earlier lower energy levels while emitting (EMR) radio waves and visible light. (I think a high enough voltage emits X-rays?). And a plasma of ions from air and fuel molecules will explode (spontaneously combust) as the ions re-combine as different molecules (exhaust gases) and release their chemical bonded energy in the process. This is the ignition that starts the flame front that travels in the combustion chamber.
If insufficient arc energy is input, the chemistry of combustion fails...
In circuit breakers, the arc is generated immediately as contacts separate (incredibly high electrical stress when the gap is near to infinitely small.. well molecular dimensions...) and continues until the voltage reaches zero (as in AC breakers) or adequate arc cooling occurs to prevent a continuous path of ions (plasma) between the contacts: I.E. some resistive gas is put in the place of the conducting plasma. This plasma-cooling and substitution with interposing fluid (resistance) is sometimes generated by external means, and sometimes by a gas explosion generated by the rapid heating of the insulating medium. (e.g. oil or gas).
All good for the soul. Using the body as a conductor is never good for the body or the soul!
Cheers!
K2

I have found that depending on whom you talk to about plasma you get different answers, everyone has an opinion right. I was taught that plasma is super heated gases at or above 5,000 deg. F. high enough to create free electrons. But if that's the case then what about neon lights and such? In RADAR we used both klystrons (basically a metal tube) & magnetrons (WW2 British invention but finished by MIT) for the final amplifier but, only the klystron becomes radio active because of it's design it produces x-rays from the high voltage.

It's been my experience that the high voltage arc across the sparkplug gap does the ionizing and the current that follows burns the fuel mix in the gap to a plasma. Depending on how much joules of energy in that spark dictates the plasma temperature. The hotter one can make it the better the combustion process will be. I know with my high amp analogue ignition just doing one full load 1/4 mile run the sparkplugs start to show signs of metal transfer from the centre electrode to the ground electrode. I have never seen this transfer with even MSD's 7AL ignition or magnetos. So I am assuming my ignition is creating plasma arcs. I have a circuit schematic and documents about how to make a circuit for measuring the ionization strength/efficiency of a combustion spark when I find it I'll post it. I think if we want to continue this discussion we do it by messaging.

Anyway, back to the simple ignition. My free time has been dwindling down but, I'm trying to get things done. I bought a portable 2 channel scope kit I would like to finish and show people a inexpensive tool/aid.

Cheers
Ray

 

[Steamchick]

Thanks Ray, Interesting! That is a hell-of-a-powerful spark if you are getting metal transfer! I would have thought the metal ions are disruptive to the wellfare of the engine internals... as well as creating a very short life for the spark-plug! Is there not too much spark current? - Especially for models where spark-plugs are relatively tiny? The Champion Engineer that I advised me on plug selection testing and results, explained that the purpose of the arc is to ionise and ignite the fuel but not to erode the plug contacts, which is why they recommended copper core (for cooling the electrode) and platinum tipped plugs - which were new technology in the 1980s for longer service intervals. (Aside: Not really "new" technology, but a move away from the GM and Ford policy of "cheapest" - that gets the customer to return to the dealership most often for cheap servicing - so Dealers have more contact for selling new cars..., and the cheap servicing doesn't dissuade the customers from using the dealer for servicing. The Japanese manufacturer's marketing in the late 1980s was for MINIMAL servicing... (only annual) so customers come back to the dealers when they are more likely to see a new model that makes their car look dated... therefore buying the next year's model!).
Interested to hear more...
K2

 

[74Sprint]

Thanks Ray, Interesting! That is a hell-of-a-powerful spark if you are getting metal transfer! I would have thought the metal ions are disruptive to the wellfare of the engine internals... as well as creating a very short life for the spark-plug! Is there not too much spark current? - Especially for models where spark-plugs are relatively tiny? The Champion Engineer that I advised me on plug selection testing and results, explained that the purpose of the arc is to ionise and ignite the fuel but not to erode the plug contacts, which is why they recommended copper core (for cooling the electrode) and platinum tipped plugs - which were new technology in the 1980s for longer service intervals. (Aside: Not really "new" technology, but a move away from the GM and Ford policy of "cheapest" - that gets the customer to return to the dealership most often for cheap servicing - so Dealers have more contact for selling new cars..., and the cheap servicing doesn't dissuade the customers from using the dealer for servicing. The Japanese manufacturer's marketing in the late 1980s was for MINIMAL servicing... (only annual) so customers come back to the dealers when they are more likely to see a new model that makes their car look dated... therefore buying the next year's model!).
Interested to hear more...
K2

You have to remember that, that ignition was for automotive racing and at full power it draws 48 amps charging the coil! It will ignite a lean mix or rich mix just as easy as a stoichiometric mixture. Yes it is hard on sparkplugs but, when I tested it on my truck I turned the power down to about 66% and it was ok. To give you some idea of the power, if by chance a cylinder has a air/fuel mix in it, is at or near TDC, and it just happens to line up with the rotor, and you turn the ignition on (which causes a spark) half the time it will start the engine!!! So it's not for model engines. LOL I do have a CDI that will work down to 0.400ma that works nicely with model engines and will be presented here later as a kit.

Most dealers here, no matter what you take your car in for always want to charge you $1,000-$1,200. I went in for a recall and oil change and they came back saying I needed $1,200 work, I did the work myself which cost $60.00 for parts.

Cheers
Ray

 

[74Sprint]

So I'm finally getting to solder up my scope kit. It's a JYE Tech DSO 138 Oscilloscope DIY Kit, it's their older model that's still available on the internet at Amazon for $40.00 CDN. I've had it for a while and it's obsolete, their new version is the DSO 138mini Oscilloscope DIY Kit and it is cheaper. It can go up 200Khz and 50vpp so for what it will be used for here, it is more than enough, well we'll see eh. Here is the link to it's web page DSO 138 Scope. All the surface mount components are pre soldered so it's just the through hole stuff to solder.

I also bought a clear plastic box/case for it, safer right. It's a single channel with some neat features. I wouldn't mind trying their DSO 68 kit because you can connect to your PC and use their software to display the waveforms. I was surprised to see that they we're using a STM32F103Cx processor it's actually a mid line 32 bit ARM processor so it's got some nice specs. Anyway I'll talk more about this and let you know how the soldering went. Oh it needs a 9 volt power supply.

Ray

 

[Vietti]

Ray,

I once heard that a top fuel dragster burned off the spark plug electrodes almost immediately on the start and dieseled the rest of the way down the track-true? Also a possible factoid that the dragster engine only turned about 800 revolutions for a 1/4 mile run, the arithmetic seems to sort of support this?

John

 

[74Sprint]

Ray,

I once heard that a top fuel dragster burned off the spark plug electrodes almost immediately on the start and dieseled the rest of the way down the track-true? Also a possible factoid that the dragster engine only turned about 800 revolutions for a 1/4 mile run, the arithmetic seems to sort of support this?

John

Yes it true the plugs can burn away real quick, the plugs won't fire but they're so hot that the nitro will still ignite, they end up working like a glow plug. Nitromethane is a really weird solvent, yup that's what it really is, pour it on the ground like concrete and hit it with a hammer and it will ignite. But when it is under compression like in an engine it is very hard to light, it needs heat, which is why they usually start the engine on gasoline or alcohol depending if N/A or supercharged. Doug Doucette a local TA/D racer here was working with me on my ignition and he ran a 500CID N/A nitro burning engine, he showed me a bunch of burned plugs and the race data. You can see from the data when a plug burned away and either finished the run or went cold from the fuel. Years ago when they ran straight magnetos and fixed timing one of the problems was they couldn't really control the combustion temperature so they ran hot and when they finished the run they would throw a switch which shorted the mags out but, if there was any fuel left in the system the engine could/would keep running until it ran out of fuel. This caused several accidents when the engine would refire and the car would run into someone/something. Today they use an MSD ignition system usually the 'Grid System' and can control the timing for the whole run and usually they do the same as me and we pull timing out in third gear or the top of the run for them. The engine and sparkplug temps get to high and pulling timing out cools those temps just enough to keep detonation down and for them burning plugs but it still happens a lot.

How many RPM does a top fuel rail make in a 3.7 sec. 1,000 foot run? Well lets do the math. First the RPM of these engines is basically controlled by the load from the clutch. Most of the time these engines go from a idle of @2,000 rpm to 6,000 RPM in half a second, after 1 second it is at 7,000 RPM and never goes below that. So lets say it averages 7,000 RPM for 3.7 seconds. So 7,000/60 = 116.667 RPM per second times this by 3.7 and you get 431.667 revolutions per pass. Of course if you add in the warm up and burn out they do about 1,200 to 1,500 revolutions. If you take this out to 1320 feet (1/4 mile) the revolutions would be only about 550. This can go higher if there is a lot of slippage and the engine hits 10,000 RPM but that is dangerous. The mechanical fuel pumps can overload the cylinders with fuel and cause a hydraulic lock/boom or the engine oil overheats and breaks down causing the crank to seize boom again. I have seen this type of explosion once and all that is left is the frontend/plate and the backend/plate of the engine. Everything else is gone, there is just the ends of the block and crank ends, no rods, pistons, heads, or blower. I remember that calculation of 800 revolutions from years ago when the T/F rails were doing about 4.8 second runs and about 6,000 Hp.

Cheers
Ray

 

[Brian Hutchings]

Does anyone know about igniters, as used by Henry Ford on his Quadricycle? I'm close to finishing a 1/4 scale model and have had some advice on the ignition but I'd like, if possible, to keep it as authentic as possible. I'm not looking for performance or even long running times, if it runs for 30 seconds or so at a time then I'll be well pleassed.
Brian

 

[dsage]

So I'm finally getting to solder up my scope kit. It's a JYE Tech DSO 138 Oscilloscope DIY Kit, it's their older model that's still available on the internet at Amazon for $40.00 CDN. I've had it for a while and it's obsolete, their new version is the DSO 138mini Oscilloscope DIY Kit and it is cheaper. It can go up 200Khz and 50vpp so for what it will be used for here, it is more than enough, well we'll see eh. Here is the link to it's web page DSO 138 Scope. All the surface mount components are pre soldered so it's just the through hole stuff to solder.
View attachment 128863View attachment 128864
I also bought a clear plastic box/case for it, safer right. It's a single channel with some neat features. I wouldn't mind trying their DSO 68 kit because you can connect to your PC and use their software to display the waveforms. I was surprised to see that they we're using a STM32F103Cx processor it's actually a mid line 32 bit ARM processor so it's got some nice specs. Anyway I'll talk more about this and let you know how the soldering went. Oh it needs a 9 volt power supply.

Ray

You'll have to make some attenuators for the input of that scope. Many things you'll measure in an ignition system are over 50v. No sense going by the way of your China coil with the scope.

 

[Bentwings]

Ray,

I once heard that a top fuel dragster burned off the spark plug electrodes almost immediately on the start and dieseled the rest of the way down the track-true? Also a possible factoid that the dragster engine only turned about 800 revolutions for a 1/4 mile run, the arithmetic seems to sort of support this?

John

Yes I drove top fuel dragster and funny cars but not the modern day ones. Even back then on a hard run the plugs would be burned off at the end of the run. Looking at them you could tell how bad the rest of the engine was. Burned pistons were common . We didn’t replace everything every run like today but often enough. Today al of them have onboard data logging so all you have donis look at the data and interpret it. Driving down the road we often played calculator numbers as these were relatively new devices. It doesn’t take long to arrange number against time to get how many revolution the engine turns knowing tire size and gear ratios. Total run life was about 3 minutes if all 8 pistons survived. Even back then cranks lasted only 20 runs or so for the very best that were about 5 grand then. Aluminum rods were good for 5 runs you could send them back for reconditioning once maybe. They have sedated cap surfaces so you can’t practically do them yourself few shops had tooling to do this. They often were out of round of wrist pin holes beat up so rods were expendable. If you were lucky a spun bearing crank could be repaired by a good crank shop. Cranks get twisted too John force’s tuner put onboard testing device Ed snd proved this years ago. Even cams twisted and caused valve issues. That’s why gear driven cams became standard. Vale springs went from 300 pounds on the seat to way over 800 pounds open. Push rods were made custom tapered with varied wall thickness an incredible expense back then the entire drive line became custom made from exotic materials. The rear axel tube now is bigger than a big guy arm made from 300m mar aging steel even it gets twisted. Gears are custom made too. There are no junkyard pars on these cars today. Funny car bodies used to be about 4 grand now they are carbon fiber and 30 grand or more add about 30 more grand to mount it few are painted but wrapped now days. Even nostalgia cars are very expensive to run. I forgot the blowers. They start about 30 grand. The rotor strips last a couple runs. They can take over 10000. One thousand hp to drive there are a few blower synos often using s supercharged alcohol motor to drive them for testing. It’s amazing the belts hold up for a single fun. They are custom made too using carbon fiber material. My street rod went 30k miles on a standard 8 mm belt the pulleys were about worn out from road dust but the belt was ok. This was an old school race belt that would last ten runs in the old days. Blocks and heads ar carved from a solid block or custom forged block of aluminum they don’t use coolant they have replaceable sleeves allowing various bore sizes to be used there is a lot of fechnogy in these cars now that wasn’t even dreamed of 30 years ago. It’s like our govt money is no object. Some time take you trusty calculator any figure out how much money weighs. A new $100 bill weighs about how 1 gram . A simple way is to pose the question on the kntrernet you can get the number of semi trailers it would take to haul the proposed budget away. It’s pretty amazing.
byron

 

[Vietti]

Thanks for all the info re drag engines. I used to subscribe to Hot Rod magazine just to read about the engines and technology but it got so far from what a shade tree mechanic or someone on a small budget could do I quit the magazine.

NASCAR used to be interesting but now the engine/car specs are so tightly controlled there is virtually no difference car to car, purely a drivers race,which was the intent I guess. I used to enjoy the few years of CANAM racing in the 60's where you could run what you brung, resulted in some interesting cars like the vacuum cleaner of Jim Hall(?).

I apologize and think we have hijacked this thread too far, maybe start a new one but don't know under what heading!

John

 

[74Sprint]

You'll have to make some attenuators for the input of that scope. Many things you'll measure in an ignition system are over 50v. No sense going by the way of your China coil with the scope.

I have an old Phillips scope a PM3302 I bought it years ago. It's old and almost worn out but it's still kicking and the storage part of it usually works LOL. I have 2 1x-10x but yah I should get some attenuators. I hacked a old probe and put a precision 1 meg resistor inline, it works but don't ask about calibration or tuning it LOL. Thanks dsage for reminding me.

Ray

 

[74Sprint]

Yes I drove top fuel dragster and funny cars but not the modern day ones. Even back then on a hard run the plugs would be burned off at the end of the run. Looking at them you could tell how bad the rest of the engine was. Burned pistons were common . We didn’t replace everything every run like today but often enough. Today al of them have onboard data logging so all you have donis look at the data and interpret it. Driving down the road we often played calculator numbers as these were relatively new devices. It doesn’t take long to arrange number against time to get how many revolution the engine turns knowing tire size and gear ratios. Total run life was about 3 minutes if all 8 pistons survived. Even back then cranks lasted only 20 runs or so for the very best that were about 5 grand then. Aluminum rods were good for 5 runs you could send them back for reconditioning once maybe. They have sedated cap surfaces so you can’t practically do them yourself few shops had tooling to do this. They often were out of round of wrist pin holes beat up so rods were expendable. If you were lucky a spun bearing crank could be repaired by a good crank shop. Cranks get twisted too John force’s tuner put onboard testing device Ed snd proved this years ago. Even cams twisted and caused valve issues. That’s why gear driven cams became standard. Vale springs went from 300 pounds on the seat to way over 800 pounds open. Push rods were made custom tapered with varied wall thickness an incredible expense back then the entire drive line became custom made from exotic materials. The rear axel tube now is bigger than a big guy arm made from 300m mar aging steel even it gets twisted. Gears are custom made too. There are no junkyard pars on these cars today. Funny car bodies used to be about 4 grand now they are carbon fiber and 30 grand or more add about 30 more grand to mount it few are painted but wrapped now days. Even nostalgia cars are very expensive to run. I forgot the blowers. They start about 30 grand. The rotor strips last a couple runs. They can take over 10000. One thousand hp to drive there are a few blower synos often using s supercharged alcohol motor to drive them for testing. It’s amazing the belts hold up for a single fun. They are custom made too using carbon fiber material. My street rod went 30k miles on a standard 8 mm belt the pulleys were about worn out from road dust but the belt was ok. This was an old school race belt that would last ten runs in the old days. Blocks and heads ar carved from a solid block or custom forged block of aluminum they don’t use coolant they have replaceable sleeves allowing various bore sizes to be used there is a lot of fechnogy in these cars now that wasn’t even dreamed of 30 years ago. It’s like our govt money is no object. Some time take you trusty calculator any figure out how much money weighs. A new $100 bill weighs about how 1 gram . A simple way is to pose the question on the kntrernet you can get the number of semi trailers it would take to haul the proposed budget away. It’s pretty amazing.
byron

Doug Doucette and I both agreed quick is never quick enough, you get use to the G's and speed and then you want more. So 'how fast can one afford to go' Yup I remember helping Doug change sleeves, pistons, and rods and asking him how long they last and how much doing 1 hole cost. His answer was depends on how greedy he gets for ET or about 5 runs and at the time (about 25 years ago) about $2,500 a hole which, was more than I spent on my whole car at that time. LOL
Yep glory days.

Ray

 

[Bentwings]

Thanks for all the info re drag engines. I used to subscribe to Hot Rod magazine just to read about the engines and technology but it got so far from what a shade tree mechanic or someone on a small budget could do I quit the magazine.

NASCAR used to be interesting but now the engine/car specs are so tightly controlled there is virtually no difference car to car, purely a drivers race,which was the intent I guess. I used to enjoy the few years of CANAM racing in the 60's where you could run what you brung, resulted in some interesting cars like the vacuum cleaner of Jim Hall(?).

I apologize and think we have hijacked this thread too far, maybe start a new one but don't know under what heading!

John

We went to the point of economics limit. Much of drag racing was match races depending on number of cars an program to be run. The name of the game was to make all of your laps or runs to get paid. Often the two quickest came back for a final round for some extra money. It forced you to run hard snd not breaknparts. Often the rule of the line was you had to take a green light to get round money. If you knew your car was in trouble you might get away just taking the green and hoping you didn’t do any further damage. I did this several times. One afte the clutch exploded. Parts were flying all over but as I backed up I saw the competitor push truck sitting on top of crushed starting lights I took the green hoping the rest of the drive line didn’t end up in my lap. Luckily it didn’t. I was crazy back then invincible as they say. We borrowed a complete clutch and with the next round guy crew changed it all out. I took a guess on adjustment and wound up winning the race. It basically paid for the damage. In 5 years we lost only 2 rounds but saved several with only minor damage. The extra round usually paid for the damage. Poor use of economics trading a dirt dollar bill for a clean one. Not quite but you get the idea. Lots of pistons were burned early ones were of weldable material so I welded them up and remachined the ring grooves. Pistons were about $200 each so an extra run or two allowed purchasing new ones . I did them for other guys too so I made a few dollars on the side. We didn’t have aluminum blocks and heads back then do we were slways on the lookout for a used motor. Or pair of heads. Few other parts were used. I salvaged a couple blowers that I sold as rebuilt or cores. Yeah scrounging was part of racing back then. I worked in a hot rod machine shop so I had some advantage of not having to have others do work for me. .
I’m sure there are other things to talk about form those days. There are not many of us left. Being able to recount this for others may help in some way. I hope so. If we get too far out of line I’m ok if someone wants to redirect. Just make a note.
Byron

 

[74Sprint]

Does anyone know about igniters, as used by Henry Ford on his Quadricycle? I'm close to finishing a 1/4 scale model and have had some advice on the ignition but I'd like, if possible, to keep it as authentic as possible. I'm not looking for performance or even long running times, if it runs for 30 seconds or so at a time then I'll be well pleassed.
Brian

Well I found what your looking for but you won't like it. The info below was taken from the National Center for Preservation Technology & Training and it is from a POD cast that you can read or listen to: quadricycle-questions-with-mose-and-andrew.

Here is a section of what you want: "Mose Nowland: Well, it would take a specialist to pick out the differences. There is a slight mystery about the ignition system that is a mechanical grounding system inside of the combustion chamber. We’ve never been able to look inside of his original for his design, shape, and material he used for those moving pieces. But, George had imagined what they would be. I’m sure that he’s replicated pretty darn close because there were certain geometries that had to be accomplished that could only probably end up looking alike whether it was replicated or the original."

I know that's probably not not what you wanted to read but, the ncptt will not let just anyone touch the original never mind opening it up. But most likely it used a low tension ignition system with one or two wires going into the head and you can read more about old ignition systems here: https://www.old-engine.com/magign.htm. I would like to say that when it comes to electrical or electronics not everything can be scaled down but, you can be creative.

Ray

 

[stackerjack]

So I'm finally getting to solder up my scope kit. It's a JYE Tech DSO 138 Oscilloscope DIY Kit, it's their older model that's still available on the internet at Amazon for $40.00 CDN. I've had it for a while and it's obsolete, their new version is the DSO 138mini Oscilloscope DIY Kit and it is cheaper. It can go up 200Khz and 50vpp so for what it will be used for here, it is more than enough, well we'll see eh. Here is the link to it's web page DSO 138 Scope. All the surface mount components are pre soldered so it's just the through hole stuff to solder.
View attachment 128863View attachment 128864
I also bought a clear plastic box/case for it, safer right. It's a single channel with some neat features. I wouldn't mind trying their DSO 68 kit because you can connect to your PC and use their software to display the waveforms. I was surprised to see that they we're using a STM32F103Cx processor it's actually a mid line 32 bit ARM processor so it's got some nice specs. Anyway I'll talk more about this and let you know how the soldering went. Oh it needs a 9 volt power supply.

Ray

Well Done Ray. Looks like you're onto a winer there. Great Stuff.

 

[a41capt]

Does anyone know about igniters, as used by Henry Ford on his Quadricycle? I'm close to finishing a 1/4 scale model and have had some advice on the ignition but I'd like, if possible, to keep it as authentic as possible. I'm not looking for performance or even long running times, if it runs for 30 seconds or so at a time then I'll be well pleassed.
Brian

I believe my set of plans for Leon Ridenour’s version of the kitchen sink engine outline a reasonable facsimile of an igniter. As this engine was the forerunner to his development of a workable internal combustion engine, and having some similarities to the Quadricycle engine, perhaps this type of igniter would suit your purposes.

If I remember correctly (it’s been a couple years since I built mine), he pretty much says that the builder should be prepared for some frustration in making it work. With that bit of info, I elected to go with a spark plug instead!

Good luck with your endeavor, and I hope you’ll post your completed engine running.

John W

 

[74Sprint]

The mini scope is done and I have started using it and here is my review.
So why does anyone need a scope for? Well a scope can do everything a multimeter can except measure current directly but, even that can be measured as a voltage drop across a load. Once a person gets use to and familiar with a scope IMHO you won't want to go back to a multimeter, at least not on a work bench. This is why I wanted a portable, low cost scope for doing basic work. There is a ton of mini-scopes out there and choosing one can be difficult so do your research.

Mine is from http://www.jyetech.com/ which I bought before xmas and is now obsolete but, is still available. I noticed that mine needs the firmware to be updated and from what I can tell I'll need my STMicro bootloader device to do that. I didn't think that a $40 mini-scope would be worthwhile but, I decided to give it a try. It is a DIY kit with all the surface mount components already soldered for you, nice. I have a very nice pencil point soldering iron with adjustable heat so soldering small components is fairly easy. But there was 2 components that were a bit difficult, the USB port and the switches because their pins were very close together.

The above pictures are from screen shots of the 7" display on my microscope.
The map of the component locations is not very clear, small, and fuzzy, so you spend a lot of time looking for part locations. The parts list for the SMD components is also on that map. For the parts you need to solder the list is part of the assembly instructions and is not a separate list. Speaking of which step 1-1 the resistors, it calls for 120 ohm resistors for R8, R12, and R13 but they gave me 120K ohm. I decided what the hell I'll try them but, nope the gain on the op-amps was way off. So I ended up putting 2 220 ohm resistors in parallel to make 110 ohms for the gain which worked out. When soldering boards I always start with the parts that are the lowest height or are covered up somehow and go up from there. The instructions follow the same way. I did kind of cheat when I soldered the 2 x 20 pin header. I soldered one row with wire solder and switched to paste on the other row. With the paste I just had to run the soldering iron down the row for a clean job. I try to use solder paste out of a syringe whenever I can because when the paste melts it goes straight to the pins and there is no bridging. Excellent stuff, try it if you can, a little goes a long way and it would have made soldering the USB and switches a breeze.

The soldered board.

Those unfilled holes are test points and are used when you put the board into self test mode for troubleshooting.
Finished board.

It's at this point you have to start the testing and doing the setup routine. MAKE sure you follow all of it as written.

No power supply is supplied so you need a 9v - 12v DC supply, either a wall-wart or a 9v battery but they don't supply the connecting cable for the 9v battery either. I used 12v and it does run a bit warm, but it ran for 20 hrs. straight so it's fine with 12v. One other problem I ran into was I had no signal at the 'Test signal ring' so I ended up using my function generator and a 35Hz square-wave signal for adjusting C4 & C6.

It took a bit of playing with the controls to get a nice signal displayed. It is a simple DSO or digital storage scope and I didn't expect for the price to be comparable to a $500 -$2,000 scope but, I was surprised to see it had some neat features. One is the single trigger capture, another is the on screen readouts that can be turned on and off.

So does it work? yes it does for low frequency stuff. One thing that bothered me was in the instructions it says that there is no guarantee that it will work! They should have said that before I bought it. It does take a bit of learning to make it useful though.
What you are seeing above is the output of the A1102EUA-T (BOPS of 245 Gauss) Hall-effect. I changed the Hall-effect because the one I was using (AH3366Q-P-B BOPS of 100 Gauss) was way too sensitive. To get the pulse above I had to move the magnet as fast toward and back as I could. As you can see the pulse is negative going which is the norm for most Hall-effects, almost grounding out the output. It's not showing the Freq, Cycl, PW, or the duty because I have it set for single trigger mode. What I wish I could show you is how the trailing edge moves back and forth which would change the timing but, that's coming. In my next instalment I show you the outputs of the CD4047 and the MOSFET, Transistor, and a IGBT. So is this mini-scope worth $40 ? I think so right now, I just wish the triggering was better, the case had a place to put the 9v battery, and external triggering. I hope to replace my old Phillips scope with a new DSO scope for around $600 sometime soon.

Cheers
Ray

 

[bluejets]

Ray, I've had a similar unit since the flood here in 2013 took all my workshop.
Works great.
Previously had a bench unit but this is much more portable and does the job.
Changed it to include a rechargable lithium pack and on-board charger module via mini usb all housed in a project box "glued" to the back.