“Vishay”), disclaim any and all liability for any errors, inaccuracies or incompleteness contained in any datasheet or in any other disclosure relating to any. BPW40 | Phototransistor; λp maxnm; 32V; 20°; Lens: transparent – This product is available in Transfer Multisort Elektronik. Check out our wide range of . Part, BPW Category. Description, Silicon NPN Epitaxial Phototransistor. Company, ETC. Datasheet, Download BPW40 datasheet. Quote. Find where to buy.
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The process daasheet shutter opening and closing takes a significant amount of time in relation to the overall shutter speed, and during those periods the shutter is acting as a variable aperture – both reducing the amount of light that gets through so the effective speed is shorter than the measured speed, and also affecting the recorded diffraction and depth of field.
BPW40 Datasheet PDF
Have a Happy New Year all Often in experimenters home brew circuits the component values are just something a chap had lying around. I use a period counter for the actual measurement, but plugging the sensor into a computer soundcard would do just as well. With a filter Capacitor, bleeder resistor, pull down resistor the circuit tolerance values can be large. I suggest checking the yellow pages or the web for a store near you that actually sells electronic components.
For faster shutter speeds I wouldn’t want to rely on the measured time between the shutter beginning to open and completely closing to determine the effective shutter speed. Or do we assume the current is datashret at 5mA and try to ensure the voltage drop across the phototransistor is correct to toggle the dataxheet at the collector?
Atm i’m thinking when powered up on 5V that datasjeet max forward voltage is 5V depending on the light. It relies on the phototransistor having a fast switching speed in response to seeing the light through the shutter. However, recording circuits are designed to handle a wide range of sound intensities, so values of R that are up to 10 times higher with values of C that are up to ten times smaller will probably also work, although the height of the blips in the trace would be less.
BPW40 Datasheet(PDF) – List of Unclassifed Manufacturers
Chris, You may well be right – I would never claim to know much about the engineering in a lens shutter – the information I quoted came from a camera repair guy who calibrated the shutter on an old Schneider S. He was initially using the internal pullup resistor in the Arduino which has a value of around 20K to substitute for R2. You can see the light sensitive area easily.
Wow – this is complicated stuff. As you can see in the quicky picture below, they have a flatter top than the BPW Also i don’t see a voltage drop, is that because it depends on the amount of light it is receiving? A laser pointer is just too fiddly to set up. Here are some DIY alternatives: So the value of the resistor you choose depends on how sensitive you want the datashset to be. Two other points occur to me: Exposure tests are more reliable in those circumstances.
Better electronic part stores usually have books that suggest substitions, so if they don’t have the exact part you can try their suggested substition from what they stock.
The main problem is getting the risetime of the sensor down, and in the end I chose a readymade light-sensitve switch IC, rather than use discrete components, because datasueet had datzsheet faster reaction time. I picked up 2 or 3 several years ago for playing around with but can’t tell you much about them except they’re easy to wire up to demonstrate they’re sensitive to light.
Use or pF, it doesn’t have to be too accurate for this application.
datsaheet The test circuit they show there in the spec sheet is very similar to one I’ve used before with opto-isolators, which are common components that have a little LED shining onto a phototransistor, all inside a sealed case.
Why people publish such daft and needlessly precise values, I don’t know.
Since it is the 5RC value that is important, any values of R and C that produce 5RC in the range of say microseconds should work. If the color response is different, you might have to use a different light source. But John Miller dataheet a link in his post – dating back to – for a. That datasheett it will fit into both 35mm and cameras, and can just be held behind an LF shutter. Maybe at faster speeds a different spring is active. So we need to choose a resistor that limits the current flow to 5mA, which would be 1kOhm.
In older texts us electrical engineers often used uuF for picofarads; ie pF.
Please do not ask for unpaid help via PM, use the forum. Higher resistance gives more sensitivity.
John suggested that the design is flexible about what phototransitor is used, so if you can’t find a BPW or BPW, just try what you can find. If you want to run the LED continuously then a lower current would probably be advisable. When there is no light there will be no current and Vce will be the supply voltage. You’re going about the choice of resistor for the phototransistor the wrong way. The spec sheet suggests you just want to obey voltage and current limits which are pretty liberal.
Sorry for not attaching a reference. The last page of the datasheet shows the voltage drop for other current flows so you could use this to adjust the resistor to reduce the current flow if necessary hint: In timing like a RC circuit the tolerances of R and C matter.