current through digital pot - Page 1
Forum section: electronics / projects

author: brownt
author_rank: Regular Contributor
timestamp: June 29, 2018, 11:16:48 pm
content: Hi, I am using a MCP4341 quad digital potentiometer, and I need to be able to pass 5mA through it for the current loop in a MIDI circuit.Why? The hardware cannot be altered, but I can do some software switching of signals and pass 5volts through one end of the pot to the wiper and out to a MIDI jack.However, the data sheet states 2.5mA as the maximum current through either the A, B or wiper terminals. If I switch things in software I can run some of the pots in parallel. Will that allow a higher maximum current?Or, perhaps 5mA constant is not required by MIDI?Or, is there something else that can be done?thanks

author: Siwastaja
author_rank: Super Contributor
timestamp: June 30, 2018, 08:39:22 am
content: The big question is,whydo you need a potentiometer in the digital MIDI communication?

author: brownt
author_rank: Regular Contributor
timestamp: June 30, 2018, 09:56:21 am
content: Thanks, but that is not the question, and is easy to answer. The hardware is set, and cannot be changed.The question is how can 5mA be drawn through this specific digital potentiometer?It seems that putting pots in parallel will share the current, but I would need to build the circuit to check it. And so I am asking the question here first. Anyone know?

author: Siwastaja
author_rank: Super Contributor
timestamp: June 30, 2018, 01:09:37 pm
content: Oh, that's a very easy question to answer:It cannot.Now that you have the answer to your question, you may still want actual advice to your actual problem, which requires you to open up the problem a little bit, and accept the help.

author: Bassman59
author_rank: Super Contributor
timestamp: June 30, 2018, 03:43:15 pm
content: Quote from: brownt on June 30, 2018, 09:56:21 amIs that because someone ordered a thousand boards built before a design review?

author: Zero999
author_rank: Super Contributor
timestamp: June 30, 2018, 06:19:33 pm
content: Connecting them in parallel should work, just make sure the voltage and power dissipation ratings aren't exceeded.I agree with the above: it's a bad design, but sometimes we have to resort to bodges, because it would be too expensive to correct mistakes made elsewhere.

author: Siwastaja
author_rank: Super Contributor
timestamp: June 30, 2018, 08:22:24 pm
content: Quote from: Hero999 on June 30, 2018, 06:19:33 pmTrue - but with a little more information, it's highly possible that the bodge would be something much better - for example, just replacing the whole component with a single fixed resistor, getting rid of the digital communication as well.System level information is especially critical when resorting to bodges and hacks.

author: Bassman59
author_rank: Super Contributor
timestamp: July 01, 2018, 05:35:27 am
content: Quote from: Hero999 on June 30, 2018, 06:19:33 pmIsn’t connecting pots in parallel changing the hardware, which we’ve been told can not be done?

author: brownt
author_rank: Regular Contributor
timestamp: July 01, 2018, 07:34:15 am
content: thanks for the interest. There is a quad pot in there already. It is wired in parallel and the system switches between different resistances as part of the units functionality. So, I can switch to the lowest resistance, wind the wiper up to the 5 volt end, switch the 5v through, and hopefully spread the current.