Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Micro Phototransistor datasheet.

Status
Not open for further replies.

kal.a

Member
I'm trying to locate the datasheet of the phototransistor in the pictures. The markings are BRT 124c446. The other number 8231 is different from one to the other. It is mounted on a little circuit board and was connected to a logic board which supplied the anode with +5Vdc and I tested it with that voltage at 20mA and it worked fine. My concern is that I want to run +24Vdc through the the collector and not sure that will handle that.

My internet searches turned out nothing so far.

Thanks a lot.

**broken link removed**
**broken link removed**
 
Last edited:
8231 likely means it was made in the 31st week of 1982; probably long obsolete...

what is the four digit number on the other part?
 
Last edited:
The other one I have has the number 40721

And by the wayI had two a couple of weeks ago both of which I burnt and threw away. They were made by Omron,part number EE-SX172 , and were used on the same board. Unfortunately I could not find the datasheet for that either.
 
Last edited:
Please have a look at this datasheet ee-sx198 (not the right datasheet) and tell me if I understand it correctly.

For the emitter the forward voltage 1.2-1.4 V at 30mA
As for the detector it is a bit confusing. The forward light current (If) is 20mA at 5V. But what are the numbers under the Value section which say .05mA min, 14mA max?
And what about the Collector-Emitter voltage (Vceo) of 30V listed under the absolute maximum ratings section. So which is it? 5V or 30V?


Thanks
 
Last edited:
At 30mA current through the LED, the voltage across the LED (i.e. the forward voltage) is between 1.2 and 1.4 volts.
The test conditions for the transistor are to hold 5V across its collector-emitter terminals. In this case, with 20mA flowing through the LED, the collector-emitter current will be between 0.5mA and 14mA. The 5V is across the output (phototransistor C-E), not the input LED.
The 5V C-E is just for defining the test setup. The 30V in the abs. max. ratings sections is telling you not to ever put >30V across the phototransistor C-E terminals.

Hope that helps.
 
ETO_OMERON_EE-SX198_SLOT_OPTO_SENSOR.png


Hi kal,

Hope you are well. I see you are working with photo detectors now. Well the good news is that they are quite simple to understand and work with. I am surprised that you have managed to blow some up because, under normal circumstances, that is practically impossible. The problem, I expect is that you have been placing a voltages on parts of the photo detector which has caused a large current to flow and melted the semiconductor material. In general always apply a voltage via a series resistor to limit the current. Incidentally that is a fairly good rule for many situations when you are not certain about what is going on.

Above is an extract from the Omeron EE-SX198 slot opto detector data sheet where I have physically inverted the transmitter LED in the schematic to make the operation clearer; the connections etc are still the same.

How to read a data sheet

One of the most daunting aspects in electronics is understanding component data sheets, but you are lucky; this one is simple, particularly well-written, and clear. This is not the position with certain data sheets, but in the main they are very good. The manufacturer is always keen to get his products specified in a design because that could mean sales of millions if a main line consumer product takes off, so he tries to incorporate all the data a design engineer would need. That is why data sheets are often so complex. Incidentally design engineers are never short of free samples, data, and support.

A data sheet covers various aspects of the components characteristics, physical, and electrical being the broad areas. It also covers Absolute Maximum Ratings and Electrical (and Optical in this case) Characteristics. The former are the limits: temperature, voltage, current, etc, that the device can be exposed to without damage. The latter is the performance of the component when configured as specified on the data sheet.

Photo Detector Operation

Transmissive slot photo detectors, have a light source shining from one side of the slot and a opto detector at the other side. Under normal circumstances, with nothing in the slot, light shines from the transmitter into the receiver and produces a signal at the receiver. But if something opaque is placed in the slot, light cannot reach the receiver so the signal from the receiver stops.

The transmitter is nothing more than a Light Emitting Diode (LED) and the receiver is a light sensitive transistor. Note that you may not be able to see any light from the LED because the light frequency is liable to be outside human eye capabilities, typically infrared, like a TV controller. In this application there are only two bits of information you need to know about the LED:
(1) Forward voltage (VF)
(2) Forward Current (IF)

The opto receiver is a fairly normal bipolar junction transistor (BJT) which has a window built into it. To conduct, normal BJTs require base current, but they will also conduct if light impinges on their junctions. That is what is done here. Incidentally you can convert some BJTs into opto sensors by removing the casing. There are, once again, only two characteristics you need from the data sheet for the opto sensor transistor:
(1) Current flow when light impinges on the opto transistor
(2) Voltage the opto transistor will stand

You can simply forget all the other stuff for your present work

Design
Assume you have a 5V supply line.

To operate the transmitter LED the way that the manufacturer recommends on the data sheet, you need:
(1) IF= 30mA
(2) At an IF of 30ma the VF is 1.2V to 1.4V

Taking the average VF as 1.3V, you can calculate what resistor you need between the 5V supply line and the anode of the transmitting LED by:
5V - 1.3V = 3.7V. To lose 3.7V at 30mA, R = 3.7V/30mA = 123.33 Ohms. A standard 120 Ohm resistor would be fine.

With 5V on the collector of the opto transistor the collector current would be between 500uA and 18mA depending on the particular opto sensor. Note that, in general, you must never connect a voltage to a transistor without some form of current limiting, normally a series resistor. A simple circuit could translate the collector current into a signal suitable for most applications: relay, TTL, CMOS, etc
 
Last edited:
The other one I have has the number 40721....

That negates the idea that 8231 was a manufacturing date code. They are always four digit numbers, two for the year, two for the week.
 
Thanks dougy, spec and Mike. Much appreciated.

Mike, that was a fantastic write-up with everything I needed to know.

I came to the forum looking for answers and help after I burned four of these suckers :banghead: . All I wanted to do is hook one of those up to a PLC which got me reading in electronics and experimenting with LED, Mosfets, resistors,capacitors and relays. And man am I having so much fun :D . I had the first one working well on a bread board with current limiting resistors and all and then I bought a small board with pin holes and soldered resistors and a mosfet to it and wired it to the phototransistor without testing it first and burnt the transmitter. I did this twice with two identical boards. Little did I know that the boards I bought had traces on them :D and were connecting 9 volts directly to the anode of the transmitter. No surprise they burnt.
Then I experimented some more and burnt a couple more out of sloppiness and rushing too much. But thanks to this forum I think I can do better on the next one.

Here's a **broken link removed**of what I have in mind for a similar photo transistor but one that I believe requires 5V for the transmitter. I could not find the exact components I wanted so you will have to use your imagination. D1 is a zener diode with break down voltage of 5.1V and D2 is a zener diode with a break down voltage of 12V. The photo transistor is U1 and M1 is the NPN Mosfet with l1 being the PLC input (the PLC input is sinking so I will actually have to put a resistor there too).
I also had a 10K resistor from gate to ground which messes up my voltage values at the gate and will require more trial and error so I left it out for now.


So what do you think guys, am I going to burn yet another photo transistor or will this work?

Thanks again everyone for such a great community.

Kal
 
Hi kal,

You will not blow anything up with that circuit, but unfortunately the circuit will not work. I will post a slightly modified circuit that will be safe and will work. I see you have moved from an opto sensor to an optop coupler.

spec
 
Thanks spec, please do post the circuit. I didn't move to an opto coupler I Ijust couldn't find a similar sensor in LTspice so I used the closest thing I could find.
 
Thanks spec, please do post the circuit. I didn't move to an opto coupler I Ijust couldn't find a similar sensor in LTspice so I used the closest thing I could find.
Are you in fact going to use the EE-SX198. I need to know before doing a circuit
 
Nope, I'm using the one my opening post with links to images of the sensor. I can not find a datasheet but I have the circuit board it was connected to and I measured the anode voltage and it was 5V. I haven't measured the collecter-emitter voltage yet.
 
That' right spec. I have it mounted on a DC motor which I control with a PLC and it will work as an open loop encoder. There's a slotted disc that runs through the photo transistor which will give five pulses per revolution.
 
https://www.vishay.com/docs/91291/91291.pdf

eto_2016_01_20_Iss01_OPTO_SENSOR.png
ERRATA
(1) NTE 2913 can replace the MOSFET shown
(2) This circuit is a light on configuration
(3) R16 is a gate stopper to prevent the MOSFET from oscillating. It should be mounted directly on the gate connection.
(4) the 15V Zener protects the gate of the MOSFET (+-20V max)
(5) the diode across the LED has no function and can be omitted. It simply protects the LED against reverse connection of the 24V supply.
(6) decoupling is omitted: Fit 100nF capacitor across the input 24V supply. Fit a 100nF capacitor across the output 24V supply. Fit a 1mF capacitor across the output 24V supply.
(7) Change Zener voltage to 18V
 
Last edited:
Thanks spec. Fantastic as usual. I greatly appreciate the time and detail you put in your replies. Very impressive indeed.

I take it the link to the datasheet is a hint that the Mosfet is an N-channel? (I'm using a different N-channel mosfet by the way NTE2913 but that was the one I found in LTspice).
So let's see if I'm following. The photo transistor detector is NPN which means it is switching negative signal so you put in the BC556 PNP transistor basically to invert the signal to a positive one so that we can use it on our gate at the N-Channel mosfet.
I hope I'm on the right track and please let me know.

But then this circuit would basically be the opposite of the one I posted. This one is "Light On" and mine is "Dark ON".
I'm going to wire it up in LTSpice and try it out. What software are you using by the way?
 
Thanks spec. Fantastic as usual. I greatly appreciate the time and detail you put in your replies. Very impressive indeed.

And I greatly appreciate your appreciation :happy:

I take it the link to the datasheet is a hint that the Mosfet is an N-channel? (I'm using a different N-channel MOSFET by the way NTE2913 but that was the one I found in LTspice).

I thought you were using an IRFZ44. That was why I designed it in. Data sheet link added for convenience only- no other reason. It is always handy to have backing data so you can cross refer form the schematic to component characteristics.
https://www.nteinc.com/specs/2900to2999/pdf/nte2913.pdf
Hell, kal. That is some MOSFET you have chosen: 110A. 8 mOhm. You could short-out the National Grid with that!

So let's see if I'm following. The photo transistor detector is NPN which means it is switching negative signal so you put in the BC556 PNP transistor basically to invert the signal to a positive one so that we can use it on our gate at the N-Channel MOSFET. I hope I'm on the right track and please let me know.

That is essentially correct.

But then this circuit would basically be the opposite of the one I posted. This one is "Light On" and mine is "Dark ON".

I hadn't appreciated that. I will post a dark on schematic.

I'm going to wire it up in LTSpice and try it out.

That will be interesting- hope the circuit works :wideyed:

What software are you using by the way?

Cadsoft EAGLE version 7.5.0, 64bit, light. The light license is free for non-profit private use. Version 7.5.0 is compatible with Windows 10. EAGLE is remarkably easy to use, once you are familiar with the interface that is. If you would like to give it a spin:
 
Last edited:
https://www.nteinc.com/specs/2900to2999/pdf/nte2913.pdf

ETO_2016_01_21_Iss01_OPTO_SENSOR_LIGHT_OFF.png

ERRATA
(1) Q20 should be BC546 not BC547. Note this is only in the interests of parts variety reduction. A BC547 will be fine as would many other small signal NPN transistors.
(2) Note that R21 is a gate stopper to prevent MOSFET Q23 from oscillating. R21 should be mounted directly on the gate of Q23
(3) Note 1mF = 1000uF
(4) Change Zener voltage to 18V
 
Last edited:
Thanks spec. I'm speechless.
I haven't had a chance to absorb all the information the new concepts like "decoupling". I'm sure to have lots of questions after I review it a few times. Hope you don't mind me asking so many questions.

Cheers
Kal
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top