Multi-channel high side switching - tearing my hair out a little

[Sophie Parker]

Hi all,

I'm working on a project which involves a bunch of IO between a 5V Arduino and a 24V lift panel (not in use for a real lift, don't worry). I need to switch at least 8 channels of 24V outputs, approx 50mA each, high side (they have common ground). I've made high-side PNP and P-channel MOSFET switches before, but I would like to be able to use something that's more easily got several channels in parallel. But logic level shifters all max out at about 6-7V, and I can't seem to find anything else.

Surely there is some sort of bog-ordinary multi-channel high side switch chip? all it would need is several small p-mosfets with driver transistors on them. How can I not find such a thing?!

P.S. I haven't really looked into optocouplers because I don't need the galvanic isolation, and they seem to take a fair bit of current on the photodiode side.

[andrewl]

First candidate I found was LT1161 just to give you a line to search

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[Julian Sortland]

Small 5 volt (DIL) relays?

On 16 October 2017 at 16:12, andrewl <and...@arcadius.com.au> wrote:

First candidate I found was LT1161 just to give you a line to search

Sent from my Samsung Galaxy smartphone.

-------- Original message --------

From: Sophie Parker <sophis...@cortices.me>

Date: 16/10/17 3:47 pm (GMT+10:00)

To: Robots & Dinosaurs <sydney-hackspace@googlegroups.com>

Subject: [RnD] Multi-channel high side switching - tearing my hair out a little

Hi all,

I'm working on a project which involves a bunch of IO between a 5V Arduino and a 24V lift panel (not in use for a real lift, don't worry). I need to switch at least 8 channels of 24V outputs, approx 50mA each, high side (they have common ground). I've made high-side PNP and P-channel MOSFET switches before, but I would like to be able to use something that's more easily got several channels in parallel. But logic level shifters all max out at about 6-7V, and I can't seem to find anything else.

Surely there is some sort of bog-ordinary multi-channel high side switch chip? all it would need is several small p-mosfets with driver transistors on them. How can I not find such a thing?!

P.S. I haven't really looked into optocouplers because I don't need the galvanic isolation, and they seem to take a fair bit of current on the photodiode side.

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[Madox]

Why not just a cheap relay board...?

[Gav]

Hi Sophie, 

I don't have a solution, but if you find a good one please shout out so I can bookmark it. 

My go to chip for driving lots of IO of moderate current is the TPIC595, but unfortunately that's low side only and it looks like there's no high side variants. 

It may sound inelegant (you kids and your need to have everything solid state!), but I'd consider giving relay boards a shot if you're just after something to get it working quickly

e.g.: https://www.jaycar.com.au/arduino-compatible-8-channel-relay-board/p/XC4418

Also, what makes the load common ground? Is it just a bunch of LEDS or something more complex? If so, is it possible you can flip the wires to each light socket, to make it common anode instead?

Cheers,

Gavin 

On 16 October 2017 at 20:05, Madox <mado...@gmail.com> wrote:

Why not just a cheap relay board...?

[kris]

I also don't have a solution...but possible a path to go wandering down
is PLC's since they use 24v but often need to integrate with ttl voltages.

the boards are quite cheap

http://www.icstation.com/4bit-optocoupler-isolator-level-voltage-converter-board-signal-p-8041.html

On 16/10/17 21:26, Gav wrote:
> Hi Sophie, 
>
> I don't have a solution, but if you find a good one please shout out
> so I can bookmark it. 
>
> My go to chip for driving lots of IO of moderate current is the
> TPIC595, but unfortunately that's low side only and it looks like
> there's no high side variants. 
>
> It may sound inelegant (you kids and your need to have everything
> solid state!), but I'd consider giving relay boards a shot if you're
> just after something to get it working quickly
> e.g.:
> https://www.jaycar.com.au/arduino-compatible-8-channel-relay-board/p/XC4418
>
> Also, what makes the load common ground? Is it just a bunch of LEDS or
> something more complex? If so, is it possible you can flip the wires
> to each light socket, to make it common anode instead?
>
> Cheers,
> Gavin 
>
> On 16 October 2017 at 20:05, Madox <mado...@gmail.com

> <mailto:mado...@gmail.com>> wrote:
>
> Why not just a cheap relay board...?
>
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[Matt Callow]

What about a high voltage shift register e.g. hv7620 ?

There are probably better options. I didn't do an extensive search. But that one can source 50ma at 200v

Matt

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[Kris]

I think it has to be high side

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From: Matt Callow <matt....@gmail.com>
Sent: 17 October 2017 07:47:42 GMT+11:00
To: robodino <sydney-h...@googlegroups.com>
Subject: Re: [RnD] Multi-channel high side switching - tearing my hair out a little

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[Matt Callow]

It has push pull outputs so it can work as either. I thought current source implied  high side driver, but I could be mistaken

On 17 Oct 2017 08:16, "Kris" <kr...@sleepingplanet.com> wrote:

I think it has to be high side

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From: Matt Callow <matt....@gmail.com>
Sent: 17 October 2017 07:47:42 GMT+11:00

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[Gav]

"What about a high voltage shift register e.g. hv7620 ?"

Dang it, I knew that chip looked familiar. A sister chip, the HV507 is used on the Gaudi labs OpenDrop project to get hundreds of controllable voltage lines to guide microfulidic arrays of reagents for ^Z^Z^Z^Z  make water droplets dance... for science:

https://www.youtube.com/watch?v=FKR5nrJtj08

The HV7620 chip looks awesome, but it seems to be designed for switching AC loads for plasma stuff and I'm having trouble translating the specs to other uses. Does that 500mA max @5% duty cycle mean only a 25mA steady state on a pin, or is it another value? It might just be too early in the morning for me to be trying to read datasheets. 

The QFP is also likely to be a pain to use without a custom board. Hopefully there's another chip available in a DIP package somewhere.  

Cheers,

Gavin 

[Jake Anderson]

P ch fet on the high side.
high value (100K?) pullup resistor from v+  to the P gate.
Depending on the fet and the voltage then either a straight pulldown to ground or through a resistor divider to ground to keep the gate voltage in spec.
Run that pulldown through a logic level N ch fet from ground with a current limiting resistor (optional but you in theory should) direct off your micro.

This is basically the circuit.

At 24V you might need to change R3 to say 100k and add a 100K where it says 90-nA (above the N ch fet) to keep the gate voltage at 12 volts below v+ so you don't blow up the P ch fet.

It all sounds complex but it's 5 components and the N ch fet can be tiny.

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[Matt Callow]

yeah, that's probably not the right chip for this application. But might give a starting point for a search...

[Matt Callow]

BTW, the open drop thing looks really cool.

On 17 October 2017 at 09:23, Matt Callow <matt....@gmail.com> wrote:

yeah, that's probably not the right chip for this application. But might give a starting point for a search...

[Kris]

Oh!
Push pull!
That will be handy for some of my stuff.
I did not know the term

---

From: Matt Callow <matt....@gmail.com>

Sent: 17 October 2017 08:27:00 GMT+11:00
To: robodino <sydney-h...@googlegroups.com>

[Sophie Parker]

Thanks for all the responses. Got some things to look on definitely. I was avoiding relays because A) really? in this day and age? and B) I want it smaller than a large relay board.

Valen, I could do P-channel FET circuits fine, but I want to minimise components -- I want to be able to build on stripboard, but if the only options are SMD I can whip something up. At this point I'm thinking maybe parallel H-bridge chips.

[Sophie Parker]

I am victorious with the following search: https://www.digikey.com/products/en/integrated-circuits-ics/pmic-power-distribution-switches-load-drivers/726?k=&pkeyword=&pv1291=189&pv1291=186&pv1291=445&FV=3fc007b%2C3fc007c%2C3fc00c5%2Cffe002d6%2C15c0069%2C15c0015%2C15c0016%2C15c0018%2C15c001c%2C15c0026%2C15c002f%2C15c0050%2C15c0051%2C15c0009&mnonly=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0

Toshiba TBD62783. I found it from an Arduino PLC interface board, zooming in and increasing contrast until I could read the chip label, then looking at others with similar specs on digikey.

On Monday, October 16, 2017 at 3:47:13 PM UTC+11, Sophie Parker wrote:

[Gav]

Love it. Hope the project goes well 

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[Madox]

https://au.mouser.com/ProductDetail/Toshiba/TBD62783APG/

TBD62083A for the low side equivalent.