{"id":5878,"date":"2023-07-11T13:14:45","date_gmt":"2023-07-11T18:14:45","guid":{"rendered":"https:\/\/pugix.com\/synth\/?p=5878"},"modified":"2023-07-19T07:16:13","modified_gmt":"2023-07-19T12:16:13","slug":"bi-color-led-driver-circuits","status":"publish","type":"post","link":"https:\/\/pugix.com\/synth\/bi-color-led-driver-circuits\/","title":{"rendered":"Bi-Color LED Driver Circuits"},"content":{"rendered":"\n

Need to drive a bi-color LED in one of your DIY projects? I needed some of these for the added LEDs in my Dual Benjolin project. I had a circuit in mind, one used by Ken Stone (CGS) in his version of the Serge Smooth and Stepped Generator. Here’s a version of that circuit, provided by J3RK in a discussion of LED driving<\/a> on the ModWiggler forum.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

I had gone to that MW discussion to ask if the 1K resistor on the input created a 1K load. Not surprised to find that yes it does. This circuit will work best if preceded by a direct op amp output. But I needed a circuit with a higher impedance input load.<\/p>\n\n\n\n

Mungo Enterprises<\/a> replied with the following schematics, the first with specific values and the second with formulas. D1 and D2 in the following can be separate or combined two-lead LEDS. The advantage of this circuit is the higher impedance input of 220K ohms.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n
\"\"<\/figure>\n\n\n\n

I set about breadboarding the Mungo design, looking for a maximum LED current of 20ma, which is the specification for the LEDs I used, Kingbright WP7113SRSGW, unfortunately obsolete. I had bought some newer ones, Kingbright WP57EGW, but I preferred the red color of the former. Here’s the circuit I ended up with to use in the Benjolin project. I measured the maximum current through the LED to be 17ma with a 5 volt input.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

This is the Mungo circuit with selected values. Where he has 220K, I think that anything between 220K and 470K would work fine. I used 390Ks simply because I had a lot of them. Where he used a 10pf capacitor, I used 47pf. Again, anything in that range would work. And I used a 20K instead of 22K because I had a lot more 20Ks on hand.<\/p>\n\n\n\n

As for the 330 ohm resistor, that’s the one to select to set the max LED current. The lower the value, the more current. A 1K value here might be better if the voltage being monitored can be patched in. In my usage, the input voltages are limited to +\/- 4.5V.<\/p>\n\n\n\n

Even though the Mungo design uses two more resistors, it saves having to add an additional op amp buffer in front to drive the 1K load.<\/p>\n\n\n\n

<\/p>\n","protected":false},"excerpt":{"rendered":"

Need to drive a bi-color LED in one of your DIY projects? I needed some of these for the added LEDs in my Dual Benjolin project. I had a circuit … Read More<\/a><\/p>\n","protected":false},"author":1,"featured_media":5881,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[14],"tags":[212,71],"class_list":["post-5878","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-projects","tag-benjolin","tag-diy"],"yoast_head":"\nBi-Color LED Driver Circuits - Richard Brewster's Electronic Sounds<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/pugix.com\/synth\/bi-color-led-driver-circuits\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Bi-Color LED Driver Circuits - Richard Brewster's Electronic Sounds\" \/>\n<meta property=\"og:description\" content=\"Need to drive a bi-color LED in one of your DIY projects? 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