Water Sparkplug

[Jetijs]

Hi all. I don't know where I got the 20mA using a 10mm LED on the output of the ITR8102, but I tried that test again and this time I could get max 6mA going through the LED. It was just as bright as before, I suppose I made a mistake in the earlier test. I tried to reduce the 10mm LED's resistance and got nothing more than 6mA. Then I shorted the ITR8102 output transistor emitter directly to the ground via an amp meter. It still showed only 6mA. I suppose that means that the ITR8102 is dead. It's a shame, because that was my last one and the store doesn't have them, will need to order them and wait for a week or so

[insane4evr]

Hi Gibs,
yes, you are right, I meant Anode and ground
I made some other tests. I hooked an amp meter in series with the PR26MF21NSZ resistor and it shows 5mA. That is way too low for the PR26MF21NSZ LED to open fully. If I reduce the 1k resistance to 500 Ohms, than the amp meter shows 5.4mA. Will try to lower the resistance some more and if this does not work, I will replace the PR26MF21NSZ. Then we will see
Thank you all for your suggestions

Seems that the ITR8102 is not delivering enough current.
Doing some rithmetic for ohms law:
If the output transistor of the ITR is fully on, it will drop ~.4 volt. The drop in the LED of the PR26 is ~1.2 volt. So, 12 - .4 - 1.2 = 10.4 volts roughly. 10.4 / 1K = 10.4 mA. 10.4 / 500 = 20.8 mA. What you are reading is much lower.

With ITR gap uncovered. Use voltmeter between 12 volt ground and ITR transistor emitter, and measure voltage should be theoretically 12 - .4 or 11.6 volts. Then measure between 12 volt ground and PR26 LED anode, shoudl theoretically be 1.2 volts.

Also PR26 datasheet page 9 show recommended operating conditions for its LED as 20 mA Min and 25 mA Max for device marked Rank 1. and 10 mA Min and 15 mA Max for Rank 2.
Have to check operating frequency 60 Hz max? How does this translate to your setup.

[Gibs]

Precisions

Hi Jetijs,
I went back to the datasheet and it says "absolute maximum rating 50 ma".

Considering the supply voltage at 12 volts and the led voltage around 1.3 volts, your resistor have to drop 10.7 volts, divided by 220 ohms equals not far from 50 ma. Because we know that 12 volts is theoretical and the reality is more like 14.4 volts (charging circuit voltage), that means more like a 13.1 volts drop. So I would never go under 270 ohms.

[Jetijs]

Hi Jetijs,
First, just to make shure that I get this right, did you meant "between anode and ground" ? (what is bolded in quote)

Hi Gibs,
yes, you are right, I meant Anode and ground
I made some other tests. I hooked an amp meter in series with the PR26MF21NSZ resistor and it shows 5mA. That is way too low for the PR26MF21NSZ LED to open fully. If I reduce the 1k resistance to 500 Ohms, than the amp meter shows 5.4mA. Will try to lower the resistance some more and if this does not work, I will replace the PR26MF21NSZ. Then we will see
Thank you all for your suggestions

[Gibs]

Current input

Hi all

...The problem is that the SCR does not trigger. It is strange. If I hook up a voltmeter on the output transistor of the ITR8102, I can see 12V when the timing gap goes between the switch, so no problems there. Then I hooked the voltmeter between the PR26MF21NSZ input LED cathode and the negative battery terminal and I see 11.4V, so I suppose everything is right, but the SCR does not fire. If I tap the battery terminals directly on the PR26MF21NSZ input LED wires, the SCR triggers without problems, even if I use a run down 12v battery that only gives 9V. I even tried to reduce the PR26MF21NSZ input LED resistor to 500Ohms - no change.
Any suggestions?
Thanks,
Jetijs

Hi Jetijs,
First, just to make shure that I get this right, did you meant "between anode and ground" ? (what is bolded in quote)

Second, I took a look at the datasheet that Mrbreau have sent and it seems that the diode input of your PR26MF21NSZ needs about 50 ma to operate well, so maybe you will have to replace the 1 kohms resistor by a 240 ohms one. Most of the infrared LED's pull more current than ordinary LED's.

But before trying a lower value resistor I suggest you to take a look at the current input on datasheet.

Keep up the good work.