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Old 02-22-2015, 09:12 PM
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John John is offline
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Default Controlling a voltage greater than 5V (high-side switching)

If you want to control an electrical load that requires more than 5VDC to operate, or requires more current than the MIDIWidget can provide, it is usually easiest to use a "low-side switching" technique as described here.

However, if you need to generate pulses of a fixed voltage greater than 5V, there are a few approaches.

One is to use a "high-side driver" array like the MIC2981 or UDN2981A. This is sort of the counterpart to the ULN2803A in the link above. The advantage of the xxx2981 is the simplicity, but there will be some voltage drop / power loss inside the chip.

Another approach is to use SPST reed relays tied to a common voltage source. The advantage here is that you have a physical wire making the connection, so there is almost no voltage drop across the relay terminals. The disadvantage is cost and the chore of wiring it up.

Instead of a mechanical reed relay, you can also use a photorelay like TLP222AF (with a series resistor on the LED input to limit current).

Finally, you can use a P-channel MOSFET. More on MOSFET load switching. And more.
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Last edited by John; 02-22-2015 at 09:38 PM.
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Old 06-30-2015, 06:21 PM
Cisplatin271 Cisplatin271 is offline
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Default brown-out.

Amazon sells an Arduino board for around 8-10 dollars. It runs on 5VDC, so 3 of these would fit this project pretty good, but the current pulled by more than 1 of these boards is too much for the Widget. I should have read this thread before ordering the Arduino boards, but the low side switching solution looks good, and pretty cheap. Thanks for pre-empting my question for hitting the current limit of the 5V lines with this thread. BTW.. What is the max current that can be pulled from the widget before brown-out?
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Old 07-01-2015, 01:51 AM
Cisplatin271 Cisplatin271 is offline
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Oh I should have included the detail that the arduino board has 8 relays triggered by 5v. At less than 10 dollars each, and I didn't have to solder anything is what made it attractive. That plus the low side switching solution listed by John, it makes this a very simple solution.
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