16 analog channel oscilloscope for hobbyist?

Thread Starter

DMahalko

Joined Oct 5, 2008
189
Are there any storage oscilloscope options for hobbyists with lots of analog channels, but doesn't cost US$ 20,000 ?

I've decided to embark on a silly project to try to add automatic engine start to a tiny Honda EU1000i portable electric generator. I merely need to temporarily disconnect the normal AC inverter output, and then backfeed the 3-phase alternator to drive it as a motor for about 30 seconds, to prime and start the engine...

But before I can get to that point, I am probably going to have to reverse-engineer how the generator signaling normally works. I will need to monitor and graph out the exciter field amps/volts, the 3 phases amps/volts, the shaft angle sensor amps/volts used for ignition timing, the throttle servo control, the inverter output amps/volts....

,

I'm up to about 16 analog outputs to monitor simultaneously, but I most likely don't need the gigahertz sampling speeds of the high end professional multichannel oscilloscopes.

Very slow kilohertz sample rates are probably good enough for monitoring signals in a combustion engine.

I've been vaguely contemplating that a multitrack 16 or 32 channel, 48khz audio mixer board might do pretty much all I need. I can use Audacity as a multitrack oscilloscope measurement tool, lol.

,

But are there any proper low-cost analog 16+ channel analog sampling oscilloscopes that can work for this?

Another low-cost option may be a "PC as oscilloscope" using a bunch of 4-channel PCI Express analog sampling boards in a mini-tower computer case.
 

crutschow

Joined Mar 14, 2008
30,122
backfeed the 3-phase alternator to drive it as a motor for about 30 seconds, to prime and start the engine...
Depending upon its design, I'm not sure that backfeeding the alternator will cause it to act as a motor.
And where are you getting the voltage to power the generator?
 

dl324

Joined Mar 30, 2015
14,701
But are there any proper low-cost analog 16+ channel analog sampling oscilloscopes that can work for this?
Most engineers would find a way to not need 16+ channels. My scopes from the 70's/80's could do up to 8 (with 2 quad amplifier plug-ins), but I'm more than happy with 4.

16 channel logic analyzers - sure, 16 channel scopes - nope.
 

Thread Starter

DMahalko

Joined Oct 5, 2008
189
Depending upon its design, I'm not sure that backfeeding the alternator will cause it to act as a motor.
And where are you getting the voltage to power the generator?
The Honda EU1000i has an exciter winding in the wiring diagram, so it probably can be driven as a standard 3-phase motor, unless their word for exciter means something else.

https://cdn.powerequipment.honda.com/pe/pdf/manuals/00X31Z406010.pdf
Page 71

The generator would be used to direct-power a handicapped electric trackchair, via a 24v DC switching power supply, using the lead-acid batteries to start the generator, to extend runtime and save the batteries for when quiet operation is desired.

https://actiontrackchair.com/

Remote-start eliminates the need for the wheelchair user to get out and crawl on the ground to the back side, to pull-start the generator.
 

Thread Starter

DMahalko

Joined Oct 5, 2008
189
Lol, I would have talked about the main subject matter under another thread title probably, but you asked, so.
 

Irving

Joined Jan 30, 2016
2,794
The generator would be used to direct-power a handicapped electric trackchair, via a 24v DC switching power supply, using the lead-acid batteries to start the generator, to extend runtime and save the batteries for when quiet operation is desired.
Are you serious? Do you know how much current you'll need to supply?
 

Thread Starter

DMahalko

Joined Oct 5, 2008
189
But a 3-phase motor requires 3-phase power.
You offer up only problems, not solutions. We are drifting off-topic for this forum so I will probably make a new thread in Power Electronics.

Random google search: IGBT 3-phase

Infineon - Power Driver Module IGBT 3 Phase 600 V 30 A 24-PowerDIP Module (1.028", 26.10mm)
https://www.digikey.com/en/products/detail/infineon-technologies/IKCM30F60GDXKMA1/5960142

This is probably the wrong driver, or overkill for the application. The actual power driver required will be determined by measuring the output voltage and current of the alternator phase coils and the field exciter coil, when it is operating normally and driving test loads.

This is driven by a microcontroller, which will be needed anyway to drive servos for the manual choke and fuel valve, and relays for the engine kill switch and economy mode switch.
 
Last edited:

MaxHeadRoom

Joined Jul 18, 2013
25,469
Not only do you need 3phase power, but get around the regulator, which nowadays is built into the alternator?
Not to mention bypassing the also built in/embedded 3ph full wave bridge rectifier.
 

crutschow

Joined Mar 14, 2008
30,122
You offer up only problems, not solutions.
Because you seem to be ignoring the large problems in doing this.
No sense to offer solutions if the problems are not first addressed. :rolleyes:

The amount of 3-phase power you need for starting will require a very high power circuit.
The chip you posted for that is just a minor part of the design.
By the time you are through with doing the design and building it, it likely would have been cheaper to buy an electric start generator, especially since you have no assurance that the generator can even be used as a motor.
 

nsaspook

Joined Aug 27, 2009
9,991
You offer up only problems, not solutions. We are drifting off-topic for this forum so I will probably make a new thread in Power Electronics.

Random google search: IGBT 3-phase

Infineon - Power Driver Module IGBT 3 Phase 600 V 30 A 24-PowerDIP Module (1.028", 26.10mm)
https://www.digikey.com/en/products/detail/infineon-technologies/IKCM30F60GDXKMA1/5960142

This is probably the wrong driver, or overkill for the application. The actual power driver required will be determined by measuring the output voltage and current of the alternator phase coils and the field exciter coil, when it is operating normally and driving test loads.

This is driven by a microcontroller, which will be needed anyway to drive servos for the manual choke and fuel valve, and relays for the engine kill switch and economy mode switch.
Can you write a proper 3-phase inverter program on a controller to use with that Power Driver and design/build the PCB with the needed thermal heat-sinking for that chip?

Unfortunately these are real problems that require real solutions. See you at Power Electronics.
 

Reloadron

Joined Jan 15, 2015
6,711
This is what you have. You have a tiny 900 watt generator which uses an inverter. Seriously if you want electric start the most viable solution would be to upgrade to a larger unit like the EU3000i series. Yes, it cost over twice the price of what you have. Unfortunately there is no easy way to get where you want to go. The unit you have was never designed around having electric start. It's a small 50 cc gasoline engine. The pull start is as good as it gets for this model. You can try but based on experience I have to agree with others in that this simply will not work out for you.

Back to your original question. No there are no inexpensive 16 channel oscilloscopes. Now if you want to pursue this you can start by looking at a 16 channel data logger. While not inexpensive one would likely fill your needs. With a price point of low dollars I do not see this working out for you. Even with 16 channels each trace will be difficult to read. A DI-710 from Dataq Instruments will give you 16 channels of single ended input. You are still looking at a $600 A/D.

Ron
 

Irving

Joined Jan 30, 2016
2,794
Your whole premis of powering a wheelchair from an SMPS is wrong. The use of an onboard generator to charge batteries and/or power wheelchair has been tried and dumped many times. As a permanent user of a highly customised wheelchair myself - with a 40+ mile range that recharges in under 3h - as well as an experienced electronic and mechanical engineer I know its not practical to power a wheelchair that way. The ActionTrack chairs are hopelessly optimistic about 'a 7 mile' range with their 400kg+ all-up-weight, AGM batteries, puny Curtis controllers and massively inefficient drive train.

You want solutions? If, unsurprisingly, more range is your requirement, the solution is to junk the AGM batteries and onboard charger. Happy to tell you more, if you're prepared to listen.
 

bassbindevil

Joined Jan 23, 2014
463
Here's 8 channels, but you're not going to have much resolution with 8 traces on the screen at once.
https://www.pcbway.com/project/shareproject/8_Channel_Voltage_Multiplexer_for_Oscilloscope.html
I don't know if it would be better to add a mux to an ADC or use four 4-channel I2C ADCs, like these at Adafruit. (You can probably find generic versions elsewhere for less money.)
https://www.adafruit.com/category/1013
Analog's fault-protected analog mux chip:
https://www.analog.com/en/products/adg508f.html

Maybe the solution is to rewind the generator to produce 28V... or replace it with a DC motor that can both start the engine and work as a generator. I thought that might be something that existed for military applications, but all I found was a portable 2kw unit that weighed about 150 pounds.
 

Reloadron

Joined Jan 15, 2015
6,711
On another note these units feature a battery charging output for charging 12 volt automotive batteries. This is covered on page 34 of the owners manual. The schematic (block diagram) can be found on page 71 of the owners manual and I seriously doubt applying three phase AC to the main stator winding is going to do anything. Not without anything applied to the excitation winding. All of this simply is not practical and I have to agree with Irving in post #14.

Ron
 

Thread Starter

DMahalko

Joined Oct 5, 2008
189
This is what you have. You have a tiny 900 watt generator which uses an inverter. Seriously if you want electric start the most viable solution would be to upgrade to a larger unit like the EU3000i series.
All About Circuits seems to be famous for topic drift, so I suppose we can keep talking about this here. No forum mod has yelled at me in private messaging.... yet...

Dragging around more weight is going to be counterproductive.
EU1000i dry weight - 29 lb
EU3000iS dry weight - 130 lb

The EU3000iS starting is not fully automatic as it has a manual choke and fuel valve.
The fuel valve should be closed when the engine is not running.
So it would still need modification to be started from the seated chair position, though not as extensive as the small generator.
 

Thread Starter

DMahalko

Joined Oct 5, 2008
189
On another note these units feature a battery charging output for charging 12 volt automotive batteries. This is covered on page 34 of the owners manual. The schematic (block diagram) can be found on page 71 of the owners manual and I seriously doubt applying three phase AC to the main stator winding is going to do anything. Not without anything applied to the excitation winding. All of this simply is not practical and I have to agree with Irving in post #14.
The DC charging circuit of the EU1000i is load-limited to 8 amps, probably 15 volts charging, so 120 watts maximum output, while the 3-phase is rated for 900 watts continuous, 1000 surge. The DC charging output not useful and can be ignored.

I expect the excitation winding needs power while the 3-phase is driven as a motor. If a motor/generator doesn't have permanent magnets then it will have a stator field coil. I don't see anything surprising about that.

While running with a 900 watt rated maximum load, determine the operating characteristics of the volts/amps being supplied to the excitation field coil and the output volts/amps of the 3-phase alternator windings.
 

dl324

Joined Mar 30, 2015
14,701
All About Circuits seems to be famous for topic drift, so I suppose we can keep talking about this here. No forum mod has yelled at me in private messaging.... yet...
It's your thread; you can talk about anything you want as long as it isn't a prohibited topic. If you want to keep it on topic, you can report posts you feel are taking it off topic.
 

Reloadron

Joined Jan 15, 2015
6,711
The DC charging circuit of the EU1000i is load-limited to 8 amps, probably 15 volts charging, so 120 watts maximum output, while the 3-phase is rated for 900 watts continuous, 1000 surge. The DC charging output not useful and can be ignored.

I expect the excitation winding needs power while the 3-phase is driven as a motor. If a motor/generator doesn't have permanent magnets then it will have a stator field coil. I don't see anything surprising about that.

While running with a 900 watt rated maximum load, determine the operating characteristics of the volts/amps being supplied to the excitation field coil and the output volts/amps of the 3-phase alternator windings.
Yes, I agree and the 12 VDC charging circuit also is not regulated or monitoring battery charge. I also agree somewhere out there a formula may exist to get from the max output of 900 Watts to what excitation voltage and current is needed.

Those little Honda units are really nice units. They are quiet and efficient. I just don't see an easy way to add an electric start to the model you have. Just my opinion on the practically of doing it. The larger units have the electric start feature but not the little units. You may be able to run the unit under a full load and while running look at the excitation voltage and current and even with that known I just do not see trying to use 3 phase AC applied to the stator to use the alternator as a motor starter as going well. Since the manuals are available online if you look at for example an EU3000 unit the lowest electric start in the series the electric start is a DC motor. They use a separate DC starter motor similar to other electric start generators. A high torque DC starter motor like I find on my motorcycle.

You can pursue this but I just do not see it ending well. I do wish you the best of luck with the endeavor.

Ron
 
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