I need to know what diode I need for a light set up I am working on.

The main current flow through the diode is going to be 9v going to power a 55watt roughly ??? amp bulb. There will be ocassional burts of 12 v power for when the light is flashing however I am going to wire up a seperate switched line to provide constant power to the same light on demand with 12 v power and wanted to keep that from back feeding up the line that supplies the 9v power.


simulate this circuit – Schematic created using CircuitLab

Above is the schematic, I need help figuring out what diode I need to get so I do not fry the electrical systems in a 2012 sierra

  • \$\begingroup\$ check out the new drawing, it was difficult to read the original text based drawing, so this is probably wrong. \$\endgroup\$ – placeholder May 1 '13 at 4:10
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    \$\begingroup\$ D2 is not needed - when 12V is applied the 9V power source will not be affected by 12V because of D1. 55W and 14A - this implies a voltage of 4V - are you sure this data is correct? 100 ohm lamp - this seems to be at odds with 55W and 14A too? \$\endgroup\$ – Andy aka May 1 '13 at 7:24
  • \$\begingroup\$ @ Andy I might of had my numbers wrong I do know it is a 55watt lamp I tried to estimate the amp's I am not an expert I know how to wire up pre made light systems.... however this is a mod so I am taking a shot in the dark on this one so any help or corrections would be useful. Not wiring noob... making my own circiut's for a system... very noob. Hence me coming here asking help, I dont want to fry my new truck and I know when I need help. And thank you rawbrawb for the drawing since I am at work and thank you Jon Watte for finding the diode. \$\endgroup\$ – Rich May 1 '13 at 8:25

You need something that can handle 5A at least, if it's a 55W bulb! Also, there will be about a volt of drop across those diodes. Also, you need at least 50V rating to handle load dumps when the starter is involved!

Digi-key seems to indicate 10A1CT is the cheapest through-hole that matches the specs: http://www.digikey.com/product-detail/en/10A01-T/10A01CT-ND/1922678


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