Reply by September 20, 20172017-09-20
On Monday, September 18, 2017 at 9:24:46 PM UTC+5:30, mako...@yahoo.com wrote:
> Please also note that a > > copy implemetation of the misbehaving circuit works fine. > > start swapping parts and report back when you have identified > the swapped part that "follows" the problem. > > m
The problem was with a bad 4 cm long wire. As the most popular variety of 2n#055 comes in a 1 mm thick metal case, a thicker heat shield must be used, and it is difficult to mount the two pairs of this combination on the PCB. in my case, the two transistor-heat shield pairs are mounted on a small strip of phenolic. There are short wires connecting the capacitor-diode-resistor network with the two 2N3055s. The wire to the base of one 2N3055s was bad. No bad transistors or incorrectly connected diodes.
Reply by Phil Hobbs September 19, 20172017-09-19
On 09/19/2017 12:21 AM, John Larkin wrote:
> On Mon, 18 Sep 2017 19:02:47 -0700 (PDT), pcdhobbs@gmail.com wrote: > >>> There are some FIR filter implementations, done in an FPGA, that >>> assume years of high-clock rate (trillions) of absolutely correct adds >>> and subtracts. Any errors or glitches make permanent offset or >>> end-around errors. >> >> Fixed-point adds and subtracts are error-free. Floating-point multiplication introduces quantization error, and of course floating-point adds and subtracts lose the LSBs of the smaller operand. >> >> Cheers >> >> Phil Hobbs > > A fir boxcar (sinc filter) has a FIFO and a subtractor and an > accumulator. You initialize everything to zero and start clocking. > Nothing can go wrong, someone said.
Integer adds and subtracts are exact modulo 2**N. Multiplication and division produce results with more bits than they start with, so even with extended precision FP registers, you have to round at some point. It's the rounding that produces the LSB/sqrt(12) RMS additive noise, and that's why accurate long-term numerical simulations of chaotic systems (exponential noise amplifiers) are impossible even in principle.
> That one bothers me, but it seems to always work. Emotionally, I > prefer an IIR filter with some feedback.
Symmetric FIR filters are pretty useful. IIRs can have limit cycles and stuff, so you have to be careful with them. Sometimes you can usefully factor a filter into an IIR part and a FIR part. The Footprints sensor's actual measured quantity was the first finite difference of the temperature of each pyroelectric pixel with 5 Hz sampling. There was a thermal rolloff caused by the thermal mass of the suspended film and the very low thermal conductance, so it had a weird peak with rolloffs on both sides. I was using a MCU with 902 bytes of RAM (PIC17C756A), and the inverse filter for that transfer function needed to be over 20 samples long, for each of 96 pixels, so it wouldn't fit. I worked out how to factor it into a 4-sample FIR followed by a one-pole IIR lowpass, so it all fit, though not by much. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Reply by Tim Williams September 19, 20172017-09-19
"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message 
news:ch61sc5tf34rochsoe07trsd9p8i22ee1u@4ax.com...
> A fir boxcar (sinc filter) has a FIFO and a subtractor and an > accumulator. You initialize everything to zero and start clocking. > Nothing can go wrong, someone said. > > That one bothers me, but it seems to always work. Emotionally, I > prefer an IIR filter with some feedback.
Well, if you want it normalized to another gain, you're likely to lose LSBs in that conversion. (Hopefully you perform the multiplication after the accumulator, so the error does not also accumulate.) If you want a better filter profile than sinc, you'll lose bits. A 1-3-3-1 is about as good as you can get with integer coefficients. Beyond that, you need arbitrary multiplications, and either a double width accumulator or acceptance of rounding. IIR must lose bits because of the repeated multiplications. But I suppose DSP theory isn't "worth reading". Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
Reply by John Larkin September 19, 20172017-09-19
On Mon, 18 Sep 2017 19:02:47 -0700 (PDT), pcdhobbs@gmail.com wrote:

>>There are some FIR filter implementations, done in an FPGA, that >>assume years of high-clock rate (trillions) of absolutely correct adds >>and subtracts. Any errors or glitches make permanent offset or >>end-around errors. > >Fixed-point adds and subtracts are error-free. Floating-point multiplication introduces quantization error, and of course floating-point adds and subtracts lose the LSBs of the smaller operand. > >Cheers > >Phil Hobbs
A fir boxcar (sinc filter) has a FIFO and a subtractor and an accumulator. You initialize everything to zero and start clocking. Nothing can go wrong, someone said. That one bothers me, but it seems to always work. Emotionally, I prefer an IIR filter with some feedback. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by September 18, 20172017-09-18
>There are some FIR filter implementations, done in an FPGA, that >assume years of high-clock rate (trillions) of absolutely correct adds >and subtracts. Any errors or glitches make permanent offset or >end-around errors.
Fixed-point adds and subtracts are error-free. Floating-point multiplication introduces quantization error, and of course floating-point adds and subtracts lose the LSBs of the smaller operand. Cheers Phil Hobbs
Reply by John Larkin September 18, 20172017-09-18
On Sun, 17 Sep 2017 11:11:36 -0700 (PDT), tabbypurr@gmail.com wrote:

>On Sunday, 17 September 2017 18:58:12 UTC+1, Jim Thompson wrote: >> On Sun, 17 Sep 2017 10:12:04 -0700, John Larkin >> <jjlarkin@highlandtechnology.com> wrote: >> >On Sun, 17 Sep 2017 09:28:20 -0700, Jim Thompson >> ><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >> >>On Sun, 17 Sep 2017 09:24:16 -0700, John Larkin >> >><jjlarkin@highlandtechnology.com> wrote: >> >> >> >>[snip] >> >>> >> >>>There is an interesting, recurring psychological effect in our >> >>>business: people describe the way a circuit can work, and ignore the >> >>>many ways that it might not work. >> >> >> >>Indeed! I have a client right now arguing with me about such a "state >> >>machine". >> >> >> >> ...Jim Thompson >> > >> > >> >Me: But if it ever gets into state 14, it hangs up. >> > >> >Them: It can't get into state 14. >> >> Yep. Some people just can't handle "what ifs". >> >> ...Jim Thompson > >Limited understanding. They only get as far as how they think it oughta work. > >Them (I don't remember exact phrases, it was a long time ago): It's completely secure, there's no way in. We've gone over it all. >Me: If you cycle the power on the server it assumes all connected machines have authorisation to access whatever account they say they have access to. And due to the slightly odd electrical layout end users can remotely cycle the power. And are now doing so. > > >NT
There are some FIR filter implementations, done in an FPGA, that assume years of high-clock rate (trillions) of absolutely correct adds and subtracts. Any errors or glitches make permanent offset or end-around errors. They seem to work. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by September 18, 20172017-09-18
 Please also note that a 
> copy implemetation of the misbehaving circuit works fine.
start swapping parts and report back when you have identified the swapped part that "follows" the problem. m
Reply by September 18, 20172017-09-18
On Sunday, September 17, 2017 at 10:46:08 PM UTC+5:30, Mike Perkins wrote:
> On 17/09/2017 07:45, dakupoto@gmail.com wrote: > > On Saturday, September 16, 2017 at 8:43:39 PM UTC+5:30, Jim Thompson wrote: > >> On Fri, 15 Sep 2017 22:43:28 -0700 (PDT), dakupoto@gmail.com wrote: > >> > >>> On Friday, September 15, 2017 at 8:24:29 PM UTC+5:30, Jim Thompson wrote: > >>>> On Thu, 14 Sep 2017 21:12:45 -0700 (PDT), dakupoto@gmail.com wrote: > >>>> > >>>>> Could some electronics guru please help ? I have > >>>>> two identical(same resistor, capacitor values) > >>>>> implementations of an astable multivibrator. I am > >>>>> using the 2N3055 and each transistor drives a coil > >>>>> each of a bifilar coil, whose common terminal is > >>>>> connected to a 12 Volt 2A(max) DC power supply. > >>>>> The coils is air core. > >>>>> > >>>>> The problem is that one implementation works as > >>>>> designed, the other does not. To check if the > >>>>> oscillator is working, a pickup coil is placed > >>>>> in the vicinity and the output of this pickup > >>>>> coil is monitored via an oscilloscope. > >>>>> > >>>>> I have observed that the base voltage on one of > >>>>> the two transistors is getting 10 V pulses, > >>>>> while the the voltage on the other transistor > >>>>> base is 0.2 V. I have un-soldered and checked > >>>>> the resistors, but they are fine. I have replaced > >>>>> the two capacitors, with two new identical ones > >>>>> but no luck. > >>>>> > >>>>> Any hints/suggestions would be of immense help. > >>>>> Thanks in advance. > >>>> > >>>> A schematic would be helpful. > >>>> > >>>> ...Jim Thompson > >>>> -- > >>>> | James E.Thompson | mens | > >>>> | Analog Innovations | et | > >>>> | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | > >>>> | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | > >>>> | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | > >>>> | E-mail Icon at http://www.analog-innovations.com | 1962 | > >>>> > >>>> I'm looking for work... see my website. > >>>> > >>>> Thinking outside the box...producing elegant & economic solutions. > >>> > >>> I would be happy to supply a schematic, but then would > >>> need an email address. This Google group does not allow > >>> attachments. > >> > >> Go to my website, click on the envelope icon. Do NOT attach anything, > >> just send an E-mail. I will reply with an E-mail address you can use > >> to send the schematic. > >> > >> > >> Thinking outside the box...producing elegant & economic solutions. > > > > I did all that, but when trying to send the email with the schematic as attachment, I got an error > > message that the mail server was not responding. > > > > Please take a look at a fairly close relative of my oscillator, the last one at : > > https://electrosome.com/astable-multivibrator-transistors/ > > I'm with Jim here, we need a schematic. > > One thing that always bothers me with this circuit is the base-emitter > breakdown, where the circuit can shovel amps into the opposite > base-emitter junction. > > The fact you mention 10V spikes and 12V centre tapped coils suggests you > haven't taken into account of the 7V BE maximum rating. > > > -- > Mike Perkins > Video Solutions Ltd > www.videosolutions.ltd.uk
In my implementation, each 2N3055's emitter is grounded SEPARATELY via a 10 Ohm 10 Watt resistor to limit the collector current. So, the issue of one transistor emitter shovelling current into the other does not arise. Please also note that a copy implemetation of the misbehaving circuit works fine.
Reply by September 18, 20172017-09-18
On Sunday, September 17, 2017 at 8:33:03 PM UTC+5:30, Jim Thompson wrote:
> On Sat, 16 Sep 2017 23:45:36 -0700 (PDT), dakupoto@gmail.com wrote: > > >On Saturday, September 16, 2017 at 8:43:39 PM UTC+5:30, Jim Thompson wrote: > >> On Fri, 15 Sep 2017 22:43:28 -0700 (PDT), dakupoto@gmail.com wrote: > >> > >> >On Friday, September 15, 2017 at 8:24:29 PM UTC+5:30, Jim Thompson wrote: > >> >> On Thu, 14 Sep 2017 21:12:45 -0700 (PDT), dakupoto@gmail.com wrote: > [snip] > >> > >> Go to my website, click on the envelope icon. Do NOT attach anything, > >> just send an E-mail. I will reply with an E-mail address you can use > >> to send the schematic. > >> > >> ...Jim Thompson > [snip] > > > >I did all that, but when trying to send the email with the schematic as attachment, > > I never got you initial E-mail (without any attachment) ?? > > >I got an error > >message that the mail server was not responding. > > That would be _your_ E-mail server. > > > > >Please take a look at a fairly close relative of my oscillator, the last one at : > >https://electrosome.com/astable-multivibrator-transistors/ > > Check to see if you have the diodes reversed. > > ...Jim Thompson > -- > | James E.Thompson | mens | > | Analog Innovations | et | > | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | > | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | > | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | > | E-mail Icon at http://www.analog-innovations.com | 1962 | > > I'm looking for work... see my website. > > Thinking outside the box...producing elegant & economic solutions.
I use GMail for all personal communications and the project I am discussing here is my side work, quite different from what I do at work (telecommunication equipment firmware). I have tried using Dropbox before, but found it very wierd. I would load files, but the intended receiver would not be able to download them. Please send me a one word email to my GMail address(dakupoto@gmail.com) and then we can ' start exchanging emails.
Reply by bitrex September 17, 20172017-09-17
On 09/17/2017 12:24 PM, John Larkin wrote:
> On Sat, 16 Sep 2017 23:30:45 -0700 (PDT), dakupoto@gmail.com wrote: > >> On Saturday, September 16, 2017 at 7:07:46 AM UTC+5:30, bitrex wrote: >>> On 09/15/2017 11:02 AM, John Larkin wrote: >>>> On Thu, 14 Sep 2017 21:12:45 -0700 (PDT), dakupoto@gmail.com wrote: >>>> >>>>> Could some electronics guru please help ? I have >>>>> two identical(same resistor, capacitor values) >>>>> implementations of an astable multivibrator. I am >>>>> using the 2N3055 and each transistor drives a coil >>>>> each of a bifilar coil, whose common terminal is >>>>> connected to a 12 Volt 2A(max) DC power supply. >>>>> The coils is air core. >>>>> >>>>> The problem is that one implementation works as >>>>> designed, the other does not. To check if the >>>>> oscillator is working, a pickup coil is placed >>>>> in the vicinity and the output of this pickup >>>>> coil is monitored via an oscilloscope. >>>>> >>>>> I have observed that the base voltage on one of >>>>> the two transistors is getting 10 V pulses, >>>>> while the the voltage on the other transistor >>>>> base is 0.2 V. I have un-soldered and checked >>>>> the resistors, but they are fine. I have replaced >>>>> the two capacitors, with two new identical ones >>>>> but no luck. >>>>> >>>>> Any hints/suggestions would be of immense help. >>>>> Thanks in advance. >>>> >>>> Schematic? >>>> >>>> >>> >>> It's probably a variation on this circuit: >>> >>> <http://www.seekic.com/uploadfile/ic-circuit/s2012121103631509.gif> >>> >>> which in my experience is a PITA to get to work correctly at the best of >>> times. It's bad don't use it >> >> No, my circuit is is a loosely related to the last one at : >> https://electrosome.com/astable-multivibrator-transistors/ > > The circuit shown does have a stable state: both transistors saturated > and nothing going on. > > But it's impossible to analyze a circuit defined as loosely related to > some other circuit. > > There is an interesting, recurring psychological effect in our > business: people describe the way a circuit can work, and ignore the > many ways that it might not work. > >
OP didn't notice that the schematic I posted was more or less the same one as his, except in his version he probably has the coils taps on either side of the center connected as the collector loads. Also the one I posted has some extra resistors and diodes and if the circuit is going to work at all with an inductive load those are kinda important.