Reply to "A Handy Little PCB for Adding Marker LEDs to a Hood Diesel"

Rod StewartOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

@Rod Stewart posted:
As a matter of interest various manufacturers including K-Line used to connect engine marker leds directly to 18VAC track power, using a 1K resistor in series with two opposed 1.8mm leds (cathode to cathode). Worked just fine. Each led would be operating at 30 Hz, one on the positive voltage swing and the other on the negative swing, each at about 13ma.
Rod

I am surprised no one caught this. I got to thinking about it and suddenly realized that if two leds were wired in this manner, they would effectively block each other, and no current would flow. I tested this on the breadboard and sure enough! Reversing either one of course instantly set things right and all was well. I must have misinterpreted the circuit years ago when examining one of these in a K-Line Mikado or whatever it was. And I assumed it was correct all this time. Sorry about that! eek

Rod

11/6/219:04 PM

<ul id="{%=id%}ButtonGroup" class="button-group h-popup-buttons even-button-group even-1">
    <li id="{%=id%}Okay_buttonContainer"><a id="{%=id%}Okay" href="javascript:void(0);" class="button success no-margin-bottom h-alert-modal-ok-button" role="button">OK</a><script type="text/javascript">
        (function() {
            function {%=id%}Okay_click(event, data) {
            {%=id%}Popup.hide();
        }
        
                $('#{%=id%}Okay').on('click', {%=id%}Okay_click);
        })();
    </script></li></ul><a href="javascript:void(0);" class="close-reveal-modal" aria-label="Close Modal">&#215;</a><div class="last-modal-focus focus-utility-element" tabindex="0"></div>
</div>
<script type="text/javascript">
        (function() {
            {%=id%}Popup = new SS.Popup.ModalPopup('{%=id%}');
        })();
    </script>

Skip to main content

Membership Required

Remove From Your Block List

Manage Follow Preferences

Block

OGR Forum Supporting Membership Required

OGR Forum Supporting Membership

Help support this forum with an OGR Forum Supporting Membership.You will be able to watch the videos in the INSTRUCTIONAL VIDEO FORUM!A one-year OGR Forum Supporting Membership is only $12 per year, so sign up now!

OR

Access the ALL the OGR VIDEO FORUMS AND over 300 back issues of OGRwith a DIGITAL SUBSCRIPTION!

Please wait...

Help support this forum with an OGR Forum Supporting Membership.
You will be able to watch the videos in the INSTRUCTIONAL VIDEO FORUM!
A one-year OGR Forum Supporting Membership is only $12 per year, so sign up now!

Access the ALL the OGR VIDEO FORUMS AND over 300 back issues of OGR
with a DIGITAL SUBSCRIPTION!