Gordon wrote:Sorry, I can't spend much time on this "checking". So, what follows is not a complete critique of your post, but only a few comments about obvious items I noticed.misha680 wrote:Hi, I want to build such a virtual wall. ... Could anyone please check to see if this is correct and perhaps suggest something about these two questions? ...DigiKey links for those two look reasonable.1 x 4093...
1 x BC547...
This LED, SFH482, appears to be an 880nm wavelength device, and its in what may be an expensive metal jacket. You need a 940nm LED.That, looks like a typo, to me. It should be "78L05"; which would make it a +5Vdc regulator...."79L05" --- what is this, ...{?}You would not need it IF you truly use a five-volt power supply. I suppose 5Vdc wall-warts ARE available with regulated output voltage, but I've not noticed any that come with domestic products. If you have the supply you intend to use, just plug it into the mains and measure its no-load output voltage to see if it is greater than, say, 1.1 * 5.0V = 5.5V (for a +/- 10% regulation)....do I need it if I use a voltage-regulated power supply (wall wort) that is 5V?Sorry, I can't run through those values for you. But, I would suggest you breadboard the oscillators with variable timing resistances (multi-turn trimmers, in place of fixed resistors, two places). Set them to the ckt's nominal values, and adjust as required to seek optimum frequencies. Afterwards, measure the resistance of each trimmer and determine whether a single, standard, fixed resistance can be substituted. You might have to parallel two values to get the size you need for each timing resistance!Resistors:...{&} ... capacitors
I don't know how critical the carrier & modulation frequencies are; and, whether caps & resistors having ordinary tolerances on their nominal values, provides a good chance of success. You will either have to find this out for yourself, or depend on another member--who has been through a DIY-VWU build--to advise you.
Gordon wrote:Sorry, I can't run through those values for you. But, I would suggest you breadboard the oscillators with variable timing resistances (multi-turn trimmers, in place of fixed resistors, two places). Set them to the ckt's nominal values, and adjust as required to seek optimum frequencies. Afterwards, measure the resistance of each trimmer and determine whether a single, standard, fixed resistance can be substituted. You might have to parallel two values to get the size you need for each timing resistance!
Gordon wrote:This LED, SFH482, appears to be an 880nm wavelength device, and its in what may be an expensive metal jacket. You need a 940nm LED.
misha680 wrote:Gordon wrote:This LED, SFH482, appears to be an 880nm wavelength device, and its in what may be an expensive metal jacket. You need a 940nm LED.
I said that because, once upon a time, in a forum, far, far away, a member of that forum reported measuring spectral emissions from the VWU and Home-Base (items which were provided with Discovery Roombas). The IR-LEDs were reported peaking at 940 nm. He also was the first to publish the wave-train data emitted by those IR-LEDs. Unfortunately, he stripped all that Roomba data from his web-site just a couple years later.Btw, why the 940 nm and not 880 nm?
That is true, and I can easily agree with the patent data you dug up, since it encompasses 940 nm.It looks like the original thread schematic used the 880 nm SFH482, and per what looks like the virtual wall patent app the specs are 880-980 nm range:...
Precisely! However, it turns out to not make any sensible difference. My memory was telling me there was enough short-wave roll-off (below 940 nm) of a silicon detector's spectral response to make a difference, so I googled some data to show you. Trouble is, I showed myself! Hah!... Is 940 to get peak in this range?
Those data should have been specified with / on the schematic diagram. If not there, you will have to compute their power dissipation, and then apply some 'safety factor'. I suggest you read and understand what liamfoxtrot reported in this post:misha680 wrote:1. For resistors, how do I know which wattage to use (1/4,1/2,1,or 2 W)?
Specification data, and the circuit, is all you have to work with. The approach you outlined is not viable.misha680 wrote:I am assuming I take it from the specs of the IR emitter, I know watts = volts * amps, and from the specs for my IR emitter I'm seeing:...
misha680 wrote:...2. Second question deals with your comment & multi-turn trimmers:
Gordon wrote:...I would suggest you breadboard the oscillators with variable timing resistances ... Set them to the ckt's nominal values, and adjust as required to seek optimum frequencies. Afterwards, measure the resistance of each trimmer and determine whether a single, standard, fixed resistance can be substituted. You might have to parallel two values to get the size you need for each timing resistance!
Yes, you could use "variable capacitors", but, life would be more difficult that way. I was referring to a variable resistance. And, you ultimately found the proper type of device at Radio Shack. Think of it as a fixed-value resistor, one terminal at each end (and it is between those two terminals that its rated resistance can be measured), but, there is also a sliding contact that can be moved from end to end. That makes it possible to pick off any resistance (relative to one of the terminals) from zero to max-R, as the slider moves from one end terminal to the far end. The slider is wired out to a (generally) middle terminal. Trimmers have that slider affixed to a fine-pitch screw-thread, which makes it easy to position the slider quite accurately.misha680 wrote:...From what I understand the multi-turn trimmer is a type of potentiometer (or I guess capacitor ...
Go back to wiki-land, to find a good explanation of the potentiometer--you'll see an example of how its used to provide a variable voltage (not that its used that way for VWU work). Also look at the definition for "rheostat", since that is the form you will / may be using the trimmer. The rheostat ignores one end terminal. Only the slider and one end-terminal are connected to your circuit (as a variable resistance).misha680 wrote:...from Wikipedia ... I've only run into the potentiometer kind...
Gordon wrote:misha680 wrote:Gordon wrote:This LED, SFH482, appears to be an 880nm wavelength device, and its in what may be an expensive metal jacket. You need a 940nm LED.I said that because, once upon a time, in a forum, far, far away, a member of that forum reported measuring spectral emissions from the VWU and Home-Base (items which were provided with Discovery Roombas). The IR-LEDs were reported peaking at 940 nm. He also was the first to publish the wave-train data emitted by those IR-LEDs. Unfortunately, he stripped all that Roomba data from his web-site just a couple years later.Btw, why the 940 nm and not 880 nm?That is true, and I can easily agree with the patent data you dug up, since it encompasses 940 nm.It looks like the original thread schematic used the 880 nm SFH482, and per what looks like the virtual wall patent app the specs are 880-980 nm range:...Precisely! However, it turns out to not make any sensible difference. My memory was telling me there was enough short-wave roll-off (below 940 nm) of a silicon detector's spectral response to make a difference, so I googled some data to show you. Trouble is, I showed myself! Hah!... Is 940 to get peak in this range?Showed myself that the response curve is somewhat flat near its peak, and that detection of an 880 nm emission should result in an electrical signal that is only a few percent less than if stimulated by 940 nm of the same incident power. Here's the curve I found:
(Source: http://physics.nist.gov/Pubs/TN1421/detector.html)
You might even find some 880 nm IR-LEDs that have higher radiance power output than the 940 nm diodes, and that difference could easily swing the selection over to using the 880 nm. That's just one more thing to research for this project!
Keep in mind that rj5555 resides in Spain, and he was faced with buying any reasonable IR-LED for his DIY project. You may not be able to procure the same LED that he bought, and then you will be faced with selecting an alternate, which IS available, and which will function as intended.
Misha, that sort of thinking brings me to a point where I may now respond to your questions in your 7 October post.
First, I want to point out that I had no intention of ignoring you, but, I did forget about your project, and AFAIK, I never received notification of your previous post. So it was about 30+ days later (not until last Friday) that I serendipitously came across that aging post!
Since then, I have been mulling in my mind how to tell you that I think this DYI-VWU project may be beyond your means, i.e., your current state of EE capability. I say that because the questions you ask in that 081007 post indicate lack of hardware experience and lack of EE calculation knowledge. Knowledge that you must have, or know where to find refresher material, when you set out to alter (change wiring or use alternate components) a schematic diagram to accommodate differing conditions. Essentially, I think you are likely at the kit-building stage, where you buy a bag of parts and put them together per instructions; and, the thing works.
I don't see this DIY-VWU project falling into that category at all. Have you noticed there has been no success stories being announced from the latest builders (1oooop, et al)? Why not? Even at the start of this thread, rj said only that the circuit(s) worked, but, gave no details about how well they worked as compared to an iRbt VWU.
As I casually keep track of the evolution of this thread, I find I'm not at all convinced that enough radiant power can be emitted by the circuits being offered; and that notion is only based on seeing what iRbt EEs had to do to drive the VWU's horizontal-beam LED in their VWU (I've done no calcs along that line, because I have zero interest in fabbing a DIY-VWU (at this point in time)).
I'll address some of your 081007 questions to close out this post:Those data should have been specified with / on the schematic diagram. If not there, you will have to compute their power dissipation, and then apply some 'safety factor'. I suggest you read and understand what liamfoxtrot reported in this post:misha680 wrote:1. For resistors, how do I know which wattage to use (1/4,1/2,1,or 2 W)?
http://www.robotreviews.com/chat/viewto ... 2859#32859
...Specification data, and the circuit, is all you have to work with. The approach you outlined is not viable.misha680 wrote:I am assuming I take it from the specs of the IR emitter, I know watts = volts * amps, and from the specs for my IR emitter I'm seeing:...misha680 wrote:...2. Second question deals with your comment & multi-turn trimmers:Gordon wrote:...I would suggest you breadboard the oscillators with variable timing resistances ... Set them to the ckt's nominal values, and adjust as required to seek optimum frequencies. Afterwards, measure the resistance of each trimmer and determine whether a single, standard, fixed resistance can be substituted. You might have to parallel two values to get the size you need for each timing resistance!Yes, you could use "variable capacitors", but, life would be more difficult that way. I was referring to a variable resistance. And, you ultimately found the proper type of device at Radio Shack. Think of it as a fixed-value resistor, one terminal at each end (and it is between those two terminals that its rated resistance can be measured), but, there is also a sliding contact that can be moved from end to end. That makes it possible to pick off any resistance (relative to one of the terminals) from zero to max-R, as the slider moves from one end terminal to the far end. The slider is wired out to a (generally) middle terminal. Trimmers have that slider affixed to a fine-pitch screw-thread, which makes it easy to position the slider quite accurately.misha680 wrote:...From what I understand the multi-turn trimmer is a type of potentiometer (or I guess capacitor ...Go back to wiki-land, to find a good explanation of the potentiometer--you'll see an example of how its used to provide a variable voltage (not that its used that way for VWU work). Also look at the definition for "rheostat", since that is the form you will / may be using the trimmer. The rheostat ignores one end terminal. Only the slider and one end-terminal are connected to your circuit (as a variable resistance).misha680 wrote:...from Wikipedia ... I've only run into the potentiometer kind...
Misha, that about does it.
I want to reiterate my suggestion that this DIY-VWU project may be more involved that you can imagine. What will you do if you put it all together and find that nothing works? How will you trouble-shoot the device. You really need access to an oscillscope to see what is happening in the circuit. How will you even know when optimum frequency settings have been acquired, unless they can be measured?
You should become familiar with iRbt's version of the VWU. There's a schematic posted in this forum (page-2 of this thread has a link, I think).
You should also become familiar with the sensor module that responds to the VWU & Home-Base beams. Search for device "PL-IRM0101-3". Its not the component used in Roomba/Scooba, but, its mfr provides better tech-data in its data sheet than mfrs of similar products do.
Finally, and I am not intending to suggest that you refrain from asking for help via this forum when I say this, but, frankly I can't spare the time it would take me to tutor you throughout this project. So, if you continue with this project, and post questions, it is unlikely that I will be responding to them (exceptions being: where I have made incorrect statements, or quickie, yes/no responses). Besides, you will fare better if one of the DIY-VWU constructors provides you with information that you require.
Good fortune to you!
Very good, Misha. I too enjoy following the same modus operandi!misha680 wrote:...and am quite proud when I am in fact able to learn new skills and accomplish success in one of these projects, and I guess that's what motivates me to keep trying...
Gordon wrote:Very good, Misha. I too enjoy following the same modus operandi!misha680 wrote:...and am quite proud when I am in fact able to learn new skills and accomplish success in one of these projects, and I guess that's what motivates me to keep trying...
You are attempting to follow posted information regarding construction of a unit that will serve as an alternate to one of iRbt's VWUs. There are several reasons for which one might like to build such a device (e.g., device miniaturization, and simplification, to permit a dedicated installation; all for not too many dollars).
You are building a transmitter. To achieve success, you must have assurance that the intended receiver will be able to work with that transmitted signal. I've not seen such assurance in this DIY-thread. It was for that reason that I suggested getting acquainted with the general characteristics of the receiver ("Infrared Remote Control Receiver Module", call it "IRCRM" for short), even though we don't know the exact mfr & P/N of the IRCRM built into iRbt's robots.
Once you know what signal characteristics the IRCRM is expecting, you will better know what is required of the transmitter. Until yesterday, you would have needed an O-scope to learn the truth about that signal.
Prompted by JoeCreate's contribution to this thread, I would like to ask you whether you noticed the correct carrier frequency (38kHz) which he announced?
In my own mind I had been questioning use of "35 kHz" that was specified at the start of this thread. I have some old notes (from a 2004 vintage forum-message) that indicated a carrier at 38 kHz. Since my notes had no credentials (no trail to the source of that datum) to back them, and since rj5555 is a practicing EE (qualified, and a known source of good advice), it was then necessary to assume rj had done his own measurement. I also had no access to instrumentation by which I could measure characteristics of the wave-form.
In the meantime, some members who had attempted the DIY-VWU project found it necessary to adjust frequency. None said where the final operating point was found. ... Time passed.
Early this year, I was googling for information about Roomba's remote-control detector (trying to zone in on the "IRCRM" used in iRbt's robots). While I did not sniff out the precise component that we see built into Roomba & Scooba bumpers, I did find many, many mfrs of many, many similar units. These things are used wherever and in whatever entertainment device may be controlled via hand-held IR-remote; and, those mfrs often offer receivers which feature various options. One option is to provide units which accept different (but fixed) carrier frequencies. 35kHz and 38kHz are just two out of (at least) a half dozen choices.
Hence, one point about that variability is, rj could have been correct about the 35kHz carrier.
Earlier this year I got geared up to measure dynamic signals, so yesterday, I decided to check out the LED-driver signal in a 2004 vintage VWU (the same unit which yielded the posted schematic diagram in this forum). The scope's probe got clipped onto jumper "J3" (which is sig-out from the U1 timing IC (a 'chip-on-board' type of construction)). J3 is handy, since the PWB need not be dismounted from the VWU's housing. Sig_GND = battery-BLK terminal.
The cells in this unit were so weak, I thought the pilot LED would start blinking at any time. I could see peak signal voltage falling as testing progressed. Yet, that drooping power-supply did not perturb the sought after data--shown next.
This first image shows not only the VWU's LED-driver wave-train, but also the shows the demodulated output of a 2XXX-Roomba's IRCRM. On the plot, we see two plus pulse-packets (violet trace, in which rising voltage correlates with increasing IR-LED current), at top; and, at bottom the IRCRM's output wave (blue trace).
(top attachment)
Markers "1" & "2" on the IRCRM-signal permit evaluation of the wave's period, some 2030 ?s (vs 2000 ?s, if actually 500 Hz).
The second image was captured with factor 2.5X increase of time-scale sensitivity, which begins to resolve (what will be shown to be) the 38 kHz pulsing.
(2nd from top attachment)
Shifting plot-types now, from signal-voltage vs. time, to signal-voltage vs. frequency (and ignoring the IRCRM's wave), it is easier to mark the VWU's fundamental frequencies of carrier, and modulation wave-forms. Marker "1" tags the carrier, and "2", way off to the left, tags the 500 Hz fundamental:
(3rd from top attachment)
Looking in the table at top, where column "M1:Chan A" intersects with the "Freq." row, we see "38.03 kHz" for the marker-1 position. Marker-2 is similarly shown, but as 0.494 kHz, for the nominal 500 Hz fundamental. By zooming in, to spread lower frequencies over the full graph, the '500' Hz fundamental can be more easily picked out.
In this final image, marker-1 is affixed to the modulation's fundamental, and the table above the plot now indicates ~492 Hz.
(last attachment)
(Explanatory note: Marker-2 is affixed to a spurious frequency, as is the 'tracer dot'. I was hunting sources of disturbances causing asynchronous amplitude modulations of the VWU's output. The spurious interference appeared to be generated within the U1 IC, since neither 60Hz, or 120 Hz spectra show with any strength).
While I was well convinced (pre-measurements) that Joe's 38 kHz is correct (he has built the VW, and elsewhere reported success), I am now more convinced by actual measurement data.
Misha, it seems you now must choose between the old path, a path still filled with rocks & hard places, or the easy path laid out for you by Joe. I don't recall, from reading your posts, any statement of objectives, other than to build your own VW. So, I see questions about that missing statement. Do your goals include any of:
a) My DIY-VWU shall deflect the nominal-robot at: 1 ft < range < 9 ft, minimum.
b) My DIY-VWU shall inhibit the nominal-robot's passage through three-foot wide, or smaller, openings.
c) My DIY-VWU shall be alkaline-cell powered.
If (a) is applicable, I think I can supply additional information; but, might also ask more questions in the process!
Nice work, Misha!misha680 wrote:It works. Will post more later. Range seems to be 5-6 ft at least, ...
Buying the 5k resistor will be no problem. The question is: Will its actual resistance be close enough to use. IOW, pay attention to resistance-tolerance....potentiometer resistance reads 4.98K I will try 5 K resistor if I can find one.
Yep, that's why you used the variable resistor(s)!...Is it kosher to take resistance values from a potentiometer from my multimeter and replace potentiometer with a resistor...
Gordon wrote:Nice work, Misha!misha680 wrote:It works. Will post more later. Range seems to be 5-6 ft at least, ...Buying the 5k resistor will be no problem. The question is: Will its actual resistance be close enough to use. IOW, pay attention to resistance-tolerance....potentiometer resistance reads 4.98K I will try 5 K resistor if I can find one.Yep, that's why you used the variable resistor(s)!...Is it kosher to take resistance values from a potentiometer from my multimeter and replace potentiometer with a resistor...
Put on your thinking cap, Misha, you are the one in best position to determine that.misha680 wrote:...p.s. Oh and is 5% okay for tolerance or do I need lower?
I don't know, maybe a CMOS-logic expert will pipe up about that. But, I see something is going sour when the timing resistor in a CMOS astable oscillator is set below 10 k-ohms. Take a look on page 227 of your copy of Don Lancaster's "CMOS Cookbook". He plots a family of curves, C_t is the parameter, in a R_t vs frequency semi-log graph. Each curve is a straight line when R_t > 10k! Below that crossover, the function is not a straight line (on a semi-log plot). You figure it out.p.p.s. Also according to the comment: ...the CD4093 isn't supposed to be used with <10K resistors at 5V. Still not exactly sure where this comment came from, and the spec for mine does not say that (and plus the circuit works), but I'm just wondering if its valid or not I guess and why. ...
Gordon wrote:Put on your thinking cap, Misha, you are the one in best position to determine that.misha680 wrote:...p.s. Oh and is 5% okay for tolerance or do I need lower?
You have the physical setup to determine how far away from nominal the 38k Hz rate may drift, or be set, and still obtain a usable output from the IRCRM. Once you know the high and low limits of IRCRM operability, you can take some arbitrary, central fraction of that overall frequency span, measure variable-resistance settings which correlate with those (inside) limits, and then see whether 5% will work, or if a 1% resistor will be needed.
When you reach that point, try this resistor-calculator, since it will give you a quick way of checking what values are available in the various tolerance assignments.
You ought to find many of the other offerings at that site very useful.
A prior post indicated the 500Hz modulation rate to be less critical, hence you may avoid the parametric measurements, and go straight to the resistor calculator.I don't know, maybe a CMOS-logic expert will pipe up about that. But, I see something is going sour when the timing resistor in a CMOS astable oscillator is set below 10 k-ohms. Take a look on page 227 of your copy of Don Lancaster's "CMOS Cookbook". He plots a family of curves, C_t is the parameter, in a R_t vs frequency semi-log graph. Each curve is a straight line when R_t > 10k! Below that crossover, the function is not a straight line (on a semi-log plot). You figure it out.p.p.s. Also according to the comment: ...the CD4093 isn't supposed to be used with <10K resistors at 5V. Still not exactly sure where this comment came from, and the spec for mine does not say that (and plus the circuit works), but I'm just wondering if its valid or not I guess and why. ...
Welcome! I knew you'd like it.misha680 wrote:...Thanks that calculator link is quite handy.
"re-measure", YES, "some >10K potentiometers", not necessarily! Just find some fixed resistor(s), one or more lying about on your bench, to make up the difference, and solder it/them in series with the variable resistance. E.g., say you want to shift to a fixed 47k timing resistor; just put one, or more, fixed resistors in series with the 10k trimmer. Preset the trimmer to mid-range (~5k), and with your added value(s) summing to about 40k ohms, you would have a starting resistance of ~45k ohms, and an adjustable range of about +/-12%.You comment about the R_t <= 10K is a little worrisome for my calculations, as it means that if I replace capacitors so I can use > 10K resistors it seems I will have to find some >10K potentiometers and re-measure resistances since they won't scale using normal RC formula...
C1: 100 nF +/- 5%
R1: 17.75 kohms <== Update 18K resistor works fine
C2: 1 nF +/- 10%
R2: 14.42 kohms **
C2: 1 nF +/- 5%
R2: 14.16 kohms
Why did you not use self-test #5? Everything can be stationary.misha680 wrote:So I realized that looking at VWU detection by Roomba's motion is not very straightforward,...
I don't recall any report about specific Remote-Control details coming through the Serial Command Interface, what, exactly do you read from that source? How do the data differ from that obtained via Test-5?....I have a much better tool at hand - the Roomba SCI ...
Of course you mean 38kHz (I can't imagine why you latched onto that "38.03" value, since it was a single measurement on a single VWU, at one point in time! 38kHz is the nominal frequency to build to.)...I have my "VWU" perfectly tuned to 38.03 MhZ and...
If I were fooling with that system, I'd like to know the peak-current flowing through the IRED. That measurement requires an oscillscope with differential inputs, or two channels should work in this case.Yet my range is <= 1 ft with both the 880 nm and 950 nm LEDs...
The range simply depended on the size of the resistor I was using in front of the LED. When I put a 20ohm resistor, I get a good 6 to 8 feet. With 100ohm I was getting about 4 feet reliably.
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