Thanks again, I didn't recall that detail of the 4Mhz clock. Then I have to decide if moving to the 16f628/648 that I also have in the drawer... Not so small, but not so big as well. Pls check the specs of the Canon R6, it has a 1/8000 mechanical shutter... (for a price!!) Definitely I will stay with 1/1000 as top. Kind regards, Jes.
El sáb., 5 sept. 2020 14:59, 'Oliver Seitz' via jallib < [email protected]> escribió: > Hi again ;-) > > The 12F625 is a bit old, it has not as many features as the more recent > controllers. One of the drawbacks here is, that it has only a fixed > internal speed of 4MHz. Therefore you have only options to have Timer1 to > run at 1000, 500, 250 or 125 kHz. So, if you need to measure times longer > than 1/4s, you will have to extend the timer in software. > > But hey, give it a try for "usual" speeds between 1/30 and 1/500 and > extend it once you're there :-) > > Greets, > Kiste > > P.S.: If a digital camera exposes 1/8000s, that is the electronic shutter > speed, surely not mechanical. > > Am Samstag, 5. September 2020, 13:21:43 MESZ hat Jes < > [email protected]> Folgendes geschrieben: > > > Hi Oliver, you are right on everything. > I got some 12F675 that if not using capture mode, I think they can be used > in Timer1 gate mode (have to check it yet). > 1/8000 means 125 useconds, I put that limit because some of the modern > digital cameras have such high speeds, but in the practice for most of my > cameras 1/1000 would be more than enough, so your recommendations are fully > valid. > Regarding phototransistors, you are also right. Photodiodes are faster, > but normally they need an opamp behind to drive the digital ports. I got > some BPW40 phototransistors, with a supply of 5volt a load of 100 ohm and a > current of 5mA use to have raise and fall times of less than 50 uSec, that > I think is enough for the 1/1000 case (1 mSec, 0.05% of the signal), so at > first I'll try that. If I find any problems I'd switch over to the > photodiode. And for the lighting I can use a standard led bulb DC driven, > instead of the laser, you are right, the laser can overdrive the sensor, > and may not be necessary. > Kind regards and many thanks for the help. > Jes. > > On Sat, Sep 5, 2020 at 12:47 PM 'Oliver Seitz' via jallib < > [email protected]> wrote: > > Hi Jes! > > PIC12F1822 would be a nice candidate. 8 pins, one I2C, up to 32MHz on > Timer1. For your application I wouldn't use "Capture", but "Timer1 Gate". > > As resolution, you could think about 64µs (or 15625 Hz), it is 6.4% at > shutter 1/1000. Without crystal you won't get more garanteed than 2-3% > accuracy anyway. > > Without using interrupts, you could measure as long as (65536*64µs=) 4,19 > seconds. > > Ok, well if you have speeds down to 1/8000 (which I have never seen ;-) > can central shutters do that? ) you would need to use the interrupt method > to extend the timer. > > And... phototransistors are quite slow, especially then overdriven by > something like a laser. Might be worth thinking about using a photodiode. > > Greets, > Kiste > > Am Samstag, 5. September 2020, 12:08:40 MESZ hat Jes < > [email protected]> Folgendes geschrieben: > > > Thanks Rob. I'm not in a hurry, just learning and trying to get profit > from what I learn. > My project is a simple shutter speed meter for old film cameras (which I > collect and repair). > There is a little led laser pointing to a phototransistor sitting on the > film plane and going through the lens socket. Max shutter "speeds" (the > term is used in photography) are of 1/8000 of sec. On the other end, time > can be a long exposure of minutes or even hours, but normally measuring up > to 5 sec should be enough to certify the accuracy of the shutter. Most > pictures are taken in a range between 1/30 sec and 1/500 sec. Many old > cameras have a restricted range, not beyond 1/250 sec. > I would like to have an autonomous unit (not tied to a, computer) so I > would need only a few pins, just one for the signal and two for an small > I2C display, like the ones powered by the SSD1306 :O) > I was following the thread because that. > Now I have to find out if one of the small 12F units is able to do that. > Would be a perfect fit for my needs. > Kind regards. > Jes. > > El sáb., 5 sept. 2020 10:17, Rob CJ <[email protected]> escribió: > > Hi Jes, > > Since my previous project was finished I was thinking of prototyping this > frequency counter in JAL. My idea is to use it in combination with an > SSD1306 display and test it using the library I created for the Si5351 > although the range will be limited of this frequency counter. > > I think of making it 'auto ranging' as to increase the frequency range > indeed by changing prescaler values as you mentioned to measure lower > frequencies. I do not yet know how low it can measure. > > I might even post it on Instructables as prototype. I saw some examples > there based on Arduino but most of them are very simple, that is no > auto-ranging and so limited in the range it can handle. > > I started today, not sure how long it wil take but when it is done I will > post the source file on Jallib or on Instructables. > > BTW I will base it on a PIC16F1823 since that is the one I often use in my > projects but you can use other PICs as long as it has the capture function. > As said I do not know how long it will take so don't wait for it 🙂. > > Kind regards, > > Rob > > ------------------------------ > *Van:* [email protected] <[email protected]> namens Jesito's > μFabLab <[email protected]> > *Verzonden:* zaterdag 5 september 2020 09:55 > *Aan:* jallib <[email protected]> > *Onderwerp:* Re: [jallib] Some help needed to measure pulse length > > Many thanks Rob. I have to figure out how to do it. Is the timer working > at the MCU clock speed?. If so the 16 bit value might be too small to hold > the pulse length for i.e. a 5 sec pulse, isn't it?. I suppose some > prescaling should be done there... Have to investigate and read more on > that. > Kind regards. > Jes. > > > El jueves, 3 de septiembre de 2020 a las 18:51:51 UTC+2, > [email protected] escribió: > > Hi Jes, > > I just checked but I was mistaken, there is a procedure that calculates a > value for the timer based on a frequency. > > If you want to measure the length of a pulse you can use the capture mode > of a timer which is available in many PICs, for example the 16F1823.From > the datasheet: > Capture mode makes use of the 16-bit Timer1 > resource. When an event occurs on the CCP1 pin, the > 16-bit CCPR1H:CCPR1L register pair captures and > stores the 16-bit value of the TMR1H:TMR1L register > pair, respectively. An event is defined as one of the > following and is configured by the CCP1M<3:0> bits of > the CCP1CON register: > • Every falling edge > • Every rising edge > • Every 4th rising edge > • Every 16th rising edge > When a capture is made, the Interrupt Request Flag bit > CCP1IF of the PIR1 register is set. The interrupt flag > must be cleared in software. If another capture occurs > before the value in the CCPR1H, CCPR1L register pair > is read, the old captured value is overwritten by the new > captured value. > > Kind regards, > > Rob > > ------------------------------ > *Van:* [email protected] <[email protected]> namens Jes < > [email protected]> > *Verzonden:* donderdag 3 september 2020 13:45 > *Aan:* [email protected] <[email protected]> > *Onderwerp:* Re: [jallib] Some help needed to measure pulse length > > Thanks Rob, I look for it, just what I needed to know :0) > > El jue., 3 sept. 2020 12:01, Rob CJ <[email protected]> escribió: > > Hi Jes, > I thought there is already a Jal library to measure the width of a pulse > created by Matt. Would that do the job? > > Met vriendelijke groet, > Rob Jansen > ------------------------------ > *From:* [email protected] <[email protected]> on behalf of > Jesito's μFabLab <[email protected]> > *Sent:* Thursday, September 3, 2020 10:49:48 AM > *To:* jallib <[email protected]> > *Subject:* [jallib] Some help needed to measure pulse length > > Hello, > I'm new to JAL and I would like to measure the length of some pulses that > can be as long as 5 sec and as short as 1/8000 of second. > I have a handful of different pics, but ideally I would like to use a > small one, I just need one pin for the pulse, two more to interface to an > I2C small display and one more to reset and restart the measure. > Could anyone point me to an example that could guide me through this?. > I love the cleanless and simplicity of JAL. > Thanks in advance. > Jes. > > -- > You received this message because you are subscribed to the Google Groups > "jallib" group. > To unsubscribe from this group and stop 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