74595 PCB Design help !

Hello !

I am planing to design a 74595 pcb driving a some transistors or mosfets.
Each board will control 24v 0.25a solenoids, boards are connected together with a 30 cm cable.
the 595's will be controlled by Arduino, Here's my questions.

I need the boards to act as fast as possible, Should I use transistor or mosfets, I think mosfets a little bit faster, Right ?
Should I use Opto Couplers between 595 & transistors to protect the low voltage side ?
Any ideas how to make this board preform as best as possible ?

Thank you

74595 is obsolete! :astonished:

Use TPIC6A595s.

Speed is irrelevant for solenoids.

Paul__B:
74595 is obsolete! :astonished:

Use TPIC6A595s.

Speed is irrelevant for solenoids.

Thank you for your replay !
Hard to get TPIC6A595 here, only 74595 avb !

How many solenoids total?

The original TTL based 74595 is obsolete everywhere in the world.
The CMOS based 74HC595 is still made today as its replacement.

WattsThat:
How many solenoids total?

The original TTL based 74595 is obsolete everywhere in the world.
The CMOS based 74HC595 is still made today as its replacement.

I am talking about 74HC595, Using 74595 as a short.
And controlling about 200 solenoids
Thank you

The question of speed is irrelevant. It's only important when you're working with kHz or MHz. What solenoid could you possibly turn on and off a thousand times per second?

Since you've already transformed the mains AC down to 24V then there's no risk of any part of your circuit board transmitting anything higher than 24V to any personnel using your equipment. So you don't need optocouplers.

For me, the "performance" of the board is "how easy is it to use?" Does it have connectors that interface with the rest of your wiring? 200 solenoids (400 wires) is a lot of wire to connect to a PCB. You need to design the PCB from the beginning to tolerate mistakes and to have as much information as possible printed onto the PCB.

MorganS:
The question of speed is irrelevant. It's only important when you're working with kHz or MHz. What solenoid could you possibly turn on and off a thousand times per second?

Since you've already transformed the mains AC down to 24V then there's no risk of any part of your circuit board transmitting anything higher than 24V to any personnel using your equipment. So you don't need optocouplers.

For me, the "performance" of the board is "how easy is it to use?" Does it have connectors that interface with the rest of your wiring? 200 solenoids (400 wires) is a lot of wire to connect to a PCB. You need to design the PCB from the beginning to tolerate mistakes and to have as much information as possible printed onto the PCB.

Got your point..

Is wiring boards with 30 cm connector cases any issues ? Should I do something with it ?
Should I Put any other components on 595's ?
Dose Adding caps to output will preform better ? I am using a SMPS for the 24v supply?

Any suggestion to be a better design ?

Thank you

Albatroon:
Any suggestion to be a better design ?

See #1. :roll_eyes:

Paul__B:
See #1. :roll_eyes:

I can't get TPIC6A595 easily :slight_smile:
The only option I have is 74HC595 ics !

By the time you wire up 200 FETs, 200 diodes and similar numbers of other components, you will want to get the TPIC6A595s!

Paul__B:
By the time you wire up 200 FETs, 200 diodes and similar numbers of other components, you will want to get the TPIC6A595s!

Can it handle a CONTINUOUS LOAD of 6.5W at 24v per channel with all channels ON at the same time ?
I think this is near the limits and I'll need FET's anyway !

This board I offer can. 74HC595s controlling AOD514 N-channel MOSFETs. Designed to support 1A per transistor. Very low Rds in AOD514. Designed for easy daisychaining of controls signals from board to board.

http://www.crossroadsfencing.com/BobuinoRev17/

CrossRoads:
This board I offer can. 74HC595s controlling AOD514 N-channel MOSFETs. Designed to support 1A per transistor. Very low Rds in AOD514. Designed for easy daisychaining of controls signals from board to board.

Thank you for your offer, I looking for build them my self.

Should be fun. Or could end up being really tedious. 200 is a lot of work. I sold 18 of these to a fellow doing a large organ, and 12 to another making a light-up yellow brock road for a Wizard of Oz Play. Don't forget diodes across the coils.

CrossRoads:
Should be fun. Or could end up being really tedious. 200 is a lot of work. I sold 18 of these to a fellow doing a large organ, and 12 to another making a light-up yellow brock road for a Wizard of Oz Play. Don't forget diodes across the coils.

I wish to be fun only :slight_smile: :slight_smile:

Thank u !

Albatroon:
Hello !

I am planing to design a 74595 pcb driving a some transistors or mosfets.
Each board will control 24v 0.25a solenoids, boards are connected together with a 30 cm cable.
the 595’s will be controlled by Arduino, Here’s my questions.

I need the boards to act as fast as possible, Should I use transistor or mosfets, I think mosfets a little bit faster, Right ?
Should I use Opto Couplers between 595 & transistors to protect the low voltage side ?
Any ideas how to make this board preform as best as possible ?

Thank you

If you are operating mechanical solenoids the speed of the transistors or MOSFETs will be completely irrelevant
as both are orders of magnitude faster than mechanical systems.

Remember you need protection from inductive kick back, and this would normally involve
free-wheel diodes (such as in the ULN2803), although the TPIC6A595 has limited inductive
kickback handling (75mJ absolute maximum event) which you’d have to check is sufficient.

Do you have requirements for the speed of turn-off? - this affects the inductive protection measures

[ BTW if you can’t get TPIC6A595’s can you get ULN2803’s? ]

Albatroon:
Can it handle a CONTINUOUS LOAD of 6.5W at 24v per channel with all channels ON at the same time ?
I think this is near the limits and I'll need FET's anyway !

Did you read the datasheet?

Continuous drain current, each output, all outputs on, IDn,TA = 25°C 350 mA

And figure 8.

(What is the "6.5W" bit?)

MarkT:
BTW if you can't get TPIC6A595's can you get ULN2803's?

Dissipating 2 W with all solenoids on - may need a heatsink!

MarkT:
If you are operating mechanical solenoids the speed of the transistors or MOSFETs will be completely irrelevant
as both are orders of magnitude faster than mechanical systems.

Remember you need protection from inductive kick back, and this would normally involve
free-wheel diodes (such as in the ULN2803), although the TPIC6A595 has limited inductive
kickback handling (75mJ absolute maximum event) which you'd have to check is sufficient.

Do you have requirements for the speed of turn-off? - this affects the inductive protection measures

[ BTW if you can't get TPIC6A595's can you get ULN2803's? ]

Thank you for your response.. I had a bad experience with ULN2803, I thought that this IC can handle the amount of current I need when all ports are open, But it didn't.. I thought that every channel can handle up to 500ma.


discussion on this issue was here : here
I think I'll use now TIP122 transistors with 595's, Till i can get some TPIC6A595's

I don't know what the speed exactly is, But It in range of 10-20 ms per cycle. Should I use something more than a flyback diodes ?

Paul__B:
Did you read the datasheet?And figure 8.

I thought that this 350ma is the max for all ports, Not each one.. I'll try to find them.. Thank you

Hi,

I don't know what the speed exactly is, But It in range of 10-20 ms per cycle. Should I use something more than a flyback diodes ?

Can you explain 10-20ms per cycle.
How long is a cyccle, and are you talking about OFF-ON-OFF of 10 to 20ms?
If so then relays are not going to be very reliable or consistent in operation.

Can you tell us the application, please?
What are you doing with all that number of output ports?

Thanks.. Tom.. :slight_smile: