Simple 600ma Current source - Page 1
Forum section: electronics / beginners

author: kozlojak
author_rank: Contributor
timestamp: March 03, 2014, 06:27:53 pm
content: I am in need of a simple 600ma current source, I have been looking for days and everyone I seem to find is for low current (1-10ma) can anyone point me in the right direction?Thanks

author: michaelym
author_rank: Regular Contributor
timestamp: March 03, 2014, 06:32:33 pm
content: you can always make a simple one from discrete components

author: casinada
author_rank: Frequent Contributor
timestamp: March 03, 2014, 06:43:14 pm
content: http://www.ebay.com/itm/600mA-constant-current-source-Mean-Well-LDD-600L-for-LEDs-CCS-0-6A-/151243517053?pt=LH_DefaultDomain_0&hash=item2336d0ec7d

author: opty
author_rank: Regular Contributor
timestamp: March 03, 2014, 06:44:01 pm
content: Hi,You didn't give many details (required precision?)...Would LM317 as current source work for you?Opty

author: johnk
author_rank: Contributor
timestamp: March 03, 2014, 06:44:52 pm
content: You could simply take a low current source and modify it for you needs, but at 600mA there will probably be high losses which the resistors have to withstand.If the output-voltage is lower than your input-voltage you could look for a buck converter or if the input-voltage is lower than the output-voltage for a boost converter.If you happen to work with output-voltages of around 1V-6V (maybe even higher) you could search ebay for LED converters - they are quite cheap nowadays (but look for one with a current-limit function!!).

author: kozlojak
author_rank: Contributor
timestamp: March 03, 2014, 06:47:35 pm
content: Sorry I should add a few more details, the supply voltage wold be 3.3V And would need to drive 600mA with a 1-3 ohm load.I have no problem making one from discrete components, but again most of the ones I have seen are for low current (20ma for LED's)the LM317 will not work due to drop out voltage

author: Zepnat
author_rank: Regular Contributor
timestamp: March 03, 2014, 08:23:27 pm
content: Does it need to be 600ma, could you get away with 700ma?These are low drop out 0.1v, operate down to about 2.7v, have overload and thermal protection, simple parallel as many as needed.But they SINK current and so need to be in the negative lead.https://www.fasttech.com/products/0/10001705/1124200-amc7135-350ma-advanced-current-regulators-sot-89EDIT: datasheet herehttp://micro-bridge.com/data/ADD/AMC7135.pdf

author: PA0PBZ
author_rank: Super Contributor
timestamp: March 03, 2014, 09:15:33 pm
content: To my surprise this seems to work quite good:

author: johnk
author_rank: Contributor
timestamp: March 03, 2014, 09:47:23 pm
content: I don't know where the voltages in your picture are measured, or how the circuit works in detail, but as I said somewhere in this circuit power will be "burned".For example: With a 1ohm load you have an output-voltage of 0.6V. So if your input-voltage is 3.3V there have to drop 2.7V in the constant current source - at 0.6A that makes 1.62W (P=I*U). That's not too much, but make sure to use some chunky resistors and a transistor that can take the current that flows though it.If your power source is a battery you should really consider a converter to waste less energy.

author: IO390
author_rank: Regular Contributor
timestamp: March 03, 2014, 10:21:56 pm
content: If it's 3.3V supply voltage, are you using a lithium battery?If so, bear in mind that the voltage when fully charged is around 4V, so factor that into the design.