Jump to content
Sign in to follow this  
Yngwie

Ir Led Troubles

Recommended Posts

I have a slight poblem. I have installed 4 IR LED (ZD 1945) as my light source for the photo transistors ZD (1950). Before soldering them to my pwer, I verified that all were working. OK. After soldering, checked to see all working working, again all good. Then place them through the holes in my bridge and 2 stop working, then 5 minutes later, another one stops. Stop and start power supply again but no good. I have a 12 volt regulated power supply. Any ideas?

 

Regards

Share this post


Link to post
Share on other sites

470 OHM on each wire. Wired up in parallel. Really strange and it is bugging me as I want to finish my light bridge but .......................

Share this post


Link to post
Share on other sites
470 OHM on each wire. Wired up in parallel. Really strange and it is bugging me as I want to finish my light bridge but .......................

If you had done them is series one 330 ohm resister would have done the job and would have been simpler wiring.

 

I assume you removed them from the bridge and tested them again

 

IR's are good cos you don't have visible light but that is also bad cos you can't see where they are shining or when they are not. At least you can see when a visible light is on.

 

check this site out

 

http://led.linear1.org/led.wiz

Share this post


Link to post
Share on other sites
What size resistors are you using? 470 ohm but what wattage? You will need 1 watt resistors for reliable operation. The 1/2 watt are very close to the limit and may have burnt.

 

Phil

 

One thing to be wary of - - unregulated wall supplies of "12 Volts dc" MAY be putting out up to 16 volts in some caes, I have measured them at 13 through to 16 unloaded and 11 to 14 with medium loads- higher than we will be creating. So it pays to test your supply unloaded, and with a mild load similar to what the LEDs will bring to the circuit. You may find you need to step up one standard resistor value in your circuit to avoid "over-driving" the LEDs. Yngwie - if you overdrove your LEDs with say 14 volts AND a resistor value of 470 ohms, it is just possible you cooked them. 14 volts say at 470 ohms resistor gives a current flow of 28ma, BUT their theorectical limit is 50ma so they SHOULD have been okay. . . . . you'll still need to check for that.

 

Hey Phil I've seen you say this before about resistor wattage, but it is surely not correct. Each LED is only drawing 20ma. And each resistor in that design is only acting in situ for one LED.

 

Even acting as a "block" on a 12V supply to deliver 20ma at a forward voltage of 1.2, the flow wattage is 0.024 watt, but an actual resistor load of 0.24 (1/4 watt) - I have happliy used 1/3rd watt resistors in all the circuits I have built, and not had any go out on me. Safety factor is 1.3 times current flow resistance.

 

However, the correct resistor value for the circuit that Yngwie created is 560 ohm, so he MAY have over-driven the LEDs and may just possibly have cooked them. I have not found the Jaycar ones to be as reliable as the Dick Smiths ones. I use the Z3235 LEDs with the Z1951 photo-transistor sensors. Those sensors are SUPPOSEDLY IR ones, this is only their peak wavelength sensitivity of 800nm. In practice they are quite sensitive to daylight and have some limited sensitivity to standard fluoro tubes. I can get many of them working reliably without even turning on the light bridge . . . . go figure. - But with the bridge running they are rock solid. I actually had them "counting random laps" the other day, and couldn't figue out why for a few minutes without the light bridge running, until we realised the garage door was up and we had enough light bleeding UNDER the table to activate the LEDs from below because I hadn't black taped them in place . . . . . . Every time we moved round the table, our legs interfered with the light bleed enough to create triggers . . . . that'll teach me not to tidy up my work.

 

Aastes, I'm not convinced on using a single resistor in the line with LED's in series; as the full current draw has to go through each LED. If you wired one resistor with the 4 LEDs in PARALLEL after it, then the resistor value to enable 20ma through each LED is 135 ohms (call it 150 ohm standard value for safety.)

As Marty says iun his documant too though, LED illumination in this circuitry may be uneve. One LED may be over-driven and cook, while another may not illunate. And of course, once you "lose" one LED to open circuit, it overloads the rest, or if one goes short-circuit, the others may stop working anyway.

 

These info items are up elsewhere, but I've cobbled together my Excel sheet for calculating resistor values, and also a tech sheet given by "Marty" on this forum, which gives a nice clear summary. I THINK Marty is um . . nope, I forget his nick . . he's a guy that joined a few months ago and was looking at making a digital system.

 

LED wiring diagram courtesy of Marty

 

LED powering formula

Edited by SlotsNZ

Share this post


Link to post
Share on other sites
What size resistors are you using? 470 ohm but what wattage? You will need 1 watt resistors for reliable operation. The 1/2 watt are very close to the limit and may have burnt.

 

Phil

 

One thing to be wary of - - unregulated wall supplies of "12 Volts dc" MAY be putting out up to 16 volts in some caes, I have measured them at 13 through to 16 unloaded and 11 to 14 with medium loads- higher than we will be creating. So it pays to test your supply unloaded, and with a mild load similar to what the LEDs will bring to the circuit. You may find you need to step up one standard resistor value in your circuit to avoid "over-driving" the LEDs. Yngwie - if you overdrove your LEDs with say 14 volts AND a resistor value of 470 ohms, it is just possible you cooked them. 14 volts say at 470 ohms resistor gives a current flow of 28ma, BUT their theorectical limit is 50ma so they SHOULD have been okay. . . . . you'll still need to check for that.

 

Hey Phil I've seen you say this before about resistor wattage, but it is surely not correct. Each LED is only drawing 20ma. And each resistor in that design is only acting in situ for one LED.

 

Even acting as a "block" on a 12V supply to deliver 20ma at a forward voltage of 1.2, the flow wattage is 0.024 watt, but an actual resistor load of 0.24 (1/4 watt) - I have happliy used 1/3rd watt resistors in all the circuits I have built, and not had any go out on me. Safety factor is 1.3 times current flow resistance.

 

However, the correct resistor value for the circuit that Yngwie created is 560 ohm, so he MAY have over-driven the LEDs and may just possibly have cooked them. I have not found the Jaycar ones to be as reliable as the Dick Smiths ones. I use the Z3235 LEDs with the Z1951 photo-transistor sensors. Those sensors are SUPPOSEDLY IR ones, this is only their peak wavelength sensitivity of 800nm. In practice they are quite sensitive to daylight and have some limited sensitivity to standard fluoro tubes. I can get many of them working reliably without even turning on the light bridge . . . . go figure. - But with the bridge running they are rock solid. I actually had them "counting random laps" the other day, and couldn't figue out why for a few minutes without the light bridge running, until we realised the garage door was up and we had enough light bleeding UNDER the table to activate the LEDs from below because I hadn't black taped them in place . . . . . . Every time we moved round the table, our legs interfered with the light bleed enough to create triggers . . . . that'll teach me not to tidy up my work.

 

Aastes, I'm not convinced on using a single resistor in the line with LED's in series; as the full current draw has to go through each LED. If you wired one resistor with the 4 LEDs in PARALLEL after it, then the resistor value to enable 20ma through each LED is 135 ohms (call it 150 ohm standard value for safety.)

As Marty says iun his documant too though, LED illumination in this circuitry may be uneve. One LED may be over-driven and cook, while another may not illunate. And of course, once you "lose" one LED to open circuit, it overloads the rest, or if one goes short-circuit, the others may stop working anyway.

 

These info items are up elsewhere, but I've cobbled together my Excel sheet for calculating resistor values, and also a tech sheet given by "Marty" on this forum, which gives a nice clear summary. I THINK Marty is um . . nope, I forget his nick . . he's a guy that joined a few months ago and was looking at making a digital system.

 

LED wiring diagram courtesy of Marty

 

LED powering formula

 

 

The weird thing is SlotNZ, that i deslodered them today anc connected them again, and they all work again. But I do not want to solder them until I am sure they will nto switch off again. HMMMM

Share this post


Link to post
Share on other sites
The weird thing is SlotNZ, that i deslodered them today anc connected them again, and they all work again. But I do not want to solder them until I am sure they will nto switch off again. HMMMM

 

I know this might sound a pretty basic question to ask . . . you suuuuuuuuure you didn't get a couple of them wired backwards when you soldered them up. . . .

 

Anyway, good news is they're working again, and you haven't blown any!

 

It would be so much easier if we could see IR with the naked eye. My video camera doesn't seem to have one of those "night functions" that you can use to view the output and see if the IR is working . . . . . I've been lucky, mine always seem to work !

Edited by SlotsNZ

Share this post


Link to post
Share on other sites
The weird thing is SlotNZ, that i deslodered them today anc connected them again, and they all work again. But I do not want to solder them until I am sure they will nto switch off again. HMMMM

 

I know this might sound a pretty basic question to ask . . . you suuuuuuuuure you didn't get a couple of them wired backwards when you soldered them up. . . .

 

Anyway, good news is they're working again, and you haven't blown any!

 

It would be so much easier if we could see IR with the naked eye. My video camera doesn't seem to have one of those "night functions" that you can use to view the output and see if the IR is working . . . . . I've been lucky, mine always seem to work !

 

Certianly could have soldered one wrong or temperally shorted them out by touching bare wires after installing them

 

I must admit I ONLY use the Dick Smith Z1951's and have done for years - They are the best i have found to date.

Share this post


Link to post
Share on other sites

Well I deslodered the connections only to find one was wired wrong! ARGHHHHHHHHH. Fixed. However, what sort of range should I expect these things to work at. Mine seem to not like any distance greater than 10 cm to sense. Is this about right or should I use the z1951 as opposed to the zd 1950 I currently have.

 

Regards

Share this post


Link to post
Share on other sites
Well I deslodered the connections only to find one was wired wrong! ARGHHHHHHHHH. Fixed. However, what sort of range should I expect these things to work at. Mine seem to not like any distance greater than 10 cm to sense. Is this about right or should I use the z1951 as opposed to the zd 1950 I currently have.

 

Regards

 

Heya, 10cm seems a little bit tight - I mean you could mount then at a bit under that and cars would still clear under them . . . . but it seems a BIT tight.

I know it's a bit of a fiddle, but having noted that those particular LEDS state a maximum draw of 50ma - and having now read you FIRST post PROPERLY this time, - that your supply to them is 12 volts regulated - - why not try putting a lower value resistor on just one of them - resistors only cost pennies.

 

At present, with a 12V supply, you are pushing 23ma through each one. If you dropped to a 420 ohm resistor, you would be putting abot 26ma through them, or with a 390 ohm resistor, about 28ma through them. They'll be brighter, and might give you a bit more distance for the sensors, but should still be within reasonable tolerance.

 

OR - you could just leave the LEDs alone, and try changing to the Dick Smiths sensors I mentioned - Z1951 That Dick Smith sensor as I mentioned, is quite sensitive, and might give yu the extra throw you are looking for.

 

The Dick Smith LED is Z3235, and LOOKS identical to the Jaycar one - 5mm with a dark blue bezel, the Dick Smith SENSOR (photo-transistor) is Z1951 and is a pale green colour 3mm diameter - don't mix the two items up.

Edited by SlotsNZ

Share this post


Link to post
Share on other sites

SlotsNZ You are dropping 10.8 Volts across the resistor at 20ma. Some of the IR transmitters that I have measured draw up to 50ma.

 

As Slots and Steve said the Z1951 are the only way to go,they are a Darlington Photo transistor so are much more responsive,I have been using them for about 9 years with no problems at all.

 

Phil


Phil

 

Hobart Miniature Car Club

 

Tassie Resins

 

Email

 

 

 

 

 

 

Logos%2016_17.small_zpswkcwjf0q.jpg

Share this post


Link to post
Share on other sites

What kind of circuit are you using?

 

You can not use one resistor to feed more than one "diode" type device. Thats just poor design and you learn that in basic electronics 101. No two diodes will switch on the same. If you feed them via one resistor one diode will turn on faster/harder than the rest. This diode then takes the lion's share of current and the others are barely one. Each diode needs to be fed by one resistor.

 

The Jaycars are better than the Dick Smith stuff. The Jaycar IR TX and Rx are a matched wavelength pair. The Dick smith stuff is not which means you need to run the s#!t out of the IR Tx to get enough wavelength overlap between IR Tx and Rx.

 

Go to the following link for a discussion on optical timing. Ive designed a circuit, built and tested it.

 

http://www.auslot.com/forums/index.php?sho...=6046&st=20

 

cheers

rick1776


cheers

rick1776

Share this post


Link to post
Share on other sites

The IR transmitters are fine to be fed from one resistor as they are on all the time and the Jaycar ones I find are better. But with them in series IF one is faulty then all will not work.

We have been using the DSE Z 1951 for 9 years on Trakmate software on all the tracks down here and never had any problems with miss counting and the circuit is that simple anyone can build it. How it goes with other programs I don't know.

 

Phil


Phil

 

Hobart Miniature Car Club

 

Tassie Resins

 

Email

 

 

 

 

 

 

Logos%2016_17.small_zpswkcwjf0q.jpg

Share this post


Link to post
Share on other sites
The IR transmitters are fine to be fed from one resistor as they are on all the time and the Jaycar ones I find are better. But with them in series IF one is faulty then all will not work.

We have been using the DSE Z 1951 for 9 years on Trakmate software on all the tracks down here and never had any problems with miss counting and the circuit is that simple anyone can build it. How it goes with other programs I don't know.

 

Phil

 

Am with you PK

As for the Darling Darlingtons these lil' buggers work with every programme I have ever come across and are the easist things to work with (just wish I could source them from somewhere other than Dick Smiths

Share this post


Link to post
Share on other sites

Ok all. Had it working, tried dropping the resistor value and now they are not working (except for one) Going to DSE tomorrow but noticed that the z3235 are matched for z1956, not z1951. Should I buy the 1951 as most of you have been raving about them?

 

 

Regards

Share this post


Link to post
Share on other sites

Yes the 1951 are great! Might be an idea to buy a spare or two. The way DSE are going they will soon become a entertainment outlet and have no electronics.

 

Are you talking about the transmitters or sensors not working?

 

The sensors ( 1951) don't need any resistors. If you dropped the value of the transmitters you may have cooked them.

 

The sensors should work with a good light source over them,you can sort them and then sort the transmitters later.

 

Phil


Phil

 

Hobart Miniature Car Club

 

Tassie Resins

 

Email

 

 

 

 

 

 

Logos%2016_17.small_zpswkcwjf0q.jpg

Share this post


Link to post
Share on other sites

Guys, thanks for the tip re: z1951. I cant believe how much better these are at detecting changes in lighting compared to the jaycar ones. Now if only DSE still had electronics components nearby hmmmm...................................................

Share this post


Link to post
Share on other sites

The Z1951 has a peak sensitivity at 800nm. Thats just a little past what humans can see at the red end of the light spectrum.

 

I suspct that all the z1951 is doing is picking up the light intensity from your room lighting and not the actual LED IR which has its peak emission at 940nm. Cut the power to the IR LED or cover it. Leave the lights on in the room. Does it still "count laps" ? I suspect that the answer will be yes. Now turn off the room lights and uncover the IR LED, does it still count laps?? I suspect that the answer is no.

 

cheers

rick1776


cheers

rick1776

Share this post


Link to post
Share on other sites

Rick I can tell you the Z1951 will work in the dark with only the IR led transmitters,they are great for nightv races,don't have to have all that light from a gantry. We run night races and the guys complain that it is too dark in the shed.

 

Phil


Phil

 

Hobart Miniature Car Club

 

Tassie Resins

 

Email

 

 

 

 

 

 

Logos%2016_17.small_zpswkcwjf0q.jpg

Share this post


Link to post
Share on other sites

I have also started to build the timing system using these receivers, i use them without a lightsource

and they work fine, even tried them in the dark and they still work with only the light from the pc screen.

can i "detune these so that they are less sensitive? maybe with a resistor but unsure as to what the values

of the current or voltage ratings so i can work out what size resistor to use.

 

Also does it matter which way resistors are soldered into the wiring and is it normal for the wiring to become

extremely hot?

 

Thanks

 

Petcap

Share this post


Link to post
Share on other sites
Rick I can tell you the Z1951 will work in the dark with only the IR led transmitters,they are great for nightv races,don't have to have all that light from a gantry. We run night races and the guys complain that it is too dark in the shed.

 

Phil

 

Same experience here as Phil. They are very reliable.

 

But like Rick says, they aren't purely an IR photo interrupter/sensor, they are sensitive a fair way into the visible light spectrum, as we found when they were picking up light coming into the garage with the doors up in the daytime.

We were walking round the track to marshall with the garage doors up. I had forgotten to turn on power to the IR emitters, and the light coming into the garage through the open doors supplied enough light to keep them "on" and working, EXCEPT when we walked betwen the sensor and the garage door . I shut the garage doors and they stopped "working" without the IR emitters turned on. Remembered to turn on the emitters, and voila, they worked.

 

MAN, did that have me fooled for a few minutes.

 

Now I have a bullet proof timing system for a lit garage, or blacked out.

 

 

 

 

- Petcap, why would you want to "de-sensitive" them? So long as they are properly placed in the slot, the cars should block any light present sufficiently to work for timing.

Direction of resistors is unimportant, but the only place you should need to use them is for the LEDs.

None of the wiring should become hot at all either on the sensor or the emitter sides.

You'd best look into that, sounds like you have a short somewhere in your supply system.

Edited by SlotsNZ

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...