Another "which diode to use" Question

[boyd]

Attached is a simple part of a circuit I am designing. I am inputting several separate 12vdc inputs to a relay bank which is common to a solid state relay.



Each 12vdc input is also, prior to going to the extractor, to be taken to another source in a separate circuit. I want to stop the back flow of electricity to the other relays in order to only have the second takeoff portion of that particular relay operate.

After research I am putting a 1k ohm resistor in and a diode. Gee I have no idea of what diode to use. I have read a lot and think a Schottky Diode but do I go for one above 12vdc to avoid ANY feedback? And the fact I am only powering a solid state relay, one at a value of say 500 millivolts is the go??

I have no idea. First time user of an electrical check valve.

Any rapid replies would be most appreciated as I have to get this baby running tomorrow which is why I am running out of research time. 2100hrs here ha ha You guys will be in the AM.

Regards
Boyd

[MOD Edit ... got rid of the cursed pdf and posted an image]

 

[Bluejets]

No idea what the 1K resistors are supposed to do. As far as diodes, one can get 100v diodes 1amp for a couple of cents each. Although the voltage is important, the 100 and 400 v diodes are common. What you need to decide is whether 1amp is sufficient or whether you need to go to 3 amp. These will have about 0.7v drop at what I think your current draw will be and shouldn't be of any concern. If it is then opt out of the standard silicon diode and go for the Schottky which will probably be faster and less v-drop( around 0.2v). Have to ask..... why all the power supply units???

 

[davenn]

No idea what the 1K resistors are supposed to do.

Agreed, the resistors don't do any good, just harm, remove them

plus you are not showing relays ... which side is supposed to be the switched contacts that you should have shown ? I am assuming the top side, with the diodes but I may be wrong ??

On the right side, you are showing 12V output to secondary devices, but there isn't and can never be 12V there

the circuit as it stands really doesnt make any sense

 

[Colin Mitchell]

"What you need to decide is whether 1amp is sufficient or whether you need to go to 3 amp. "

How can 3 amps flow through a 1k resistor???????

 

[boyd]

Sorry it was a rushed drawing last night because I need to get it going today and with the time frame.

I thought I had to limit the current to each relay input the relay being SRD-12VDC-SL-C so I put in a resistor.

Multiple 12VDC inputs are one power supply installed into each machine in my workshop. They were US$1.70 each and a good way to output that a machine had been switched on, keeping the 230VAC inside the machine enclosure with only 12VDC output to my relay bank and further devices I feel is safest without having 230VAC running all around the shop for control purposes.

The takeoff on the RH side of the circuit goes to a different relay bank which is for phenmatic solenoids. Which is why the doides are there to stop operation of ALL the pneumatic side when one machine is switched on.

1.0A is plenty to drive the relays for both relay banks.

I am going to go for a silicon 100v 1A diode and ditch the resistor. Unless the relay maxes out if I put more than 1A into it? The 12VDC power supplies are small, tiny and put out I think max 2A

It was the rush and confusion of what diode to put in the circuit that mad me write this thread.

Hey people? Thanks heaps. I will report back. This is full automation of my workshop extraction system which will save me 37hrs a year ha ha ha

 

[davenn]

I thought I had to limit the current to each relay input the relay being SRD-12VDC-SL-C so I put in a resistor.

did you actually read what I wrote ??
seems not as you didn't address any of my comments or queries

AGAIN just in case you don't understand

Agreed, the resistors don't do any good, just harm, remove them

plus you are not showing relays ... which side is supposed to be the switched contacts that you should have shown ? I am assuming the top side, with the diodes but I may be wrong ??

On the right side, you are showing 12V output to secondary devices, but there isn't and can never be 12V there

the circuit as it stands really doesnt make any sense

the choice of diode is irrelevant at this time as the circuit wont work as drawn


Dave

 

[boyd]

Hi Dave. Apologies. I have Visio but it cannot connect to the internet to get the correct symbols. I even had to download a jpg of a diode.

I am removing the resistors and have chosen 400v 1A diodes.

Yes the switched contacts on the relays are at the top. The actuation of each relay is by a separate 12vdc power supply dependent on which one is activated.

In the diagram, there is a fourth 12vdc power-supply which will run across the relay contacts, also that fourth 12vdc will run to the secondary relay bank(not shown). But will be separate from the other relay contacts hence the diode. I have only shown one. Each relay will have an additional output.

All of the three (and only three shown) relay contacts will run through a 12vdc timer delay, to a 0-30v dc to 230vac relay for the HV side to run the extractor. Here is a diagram (also poorly designed and not final) of my whole project. I have put the timer in, so if I switch machines using the same extractor, it will not switch on/off rapidly but remain running.

Make sense? I have all my components and have built the pneumatic valve gate assemblies to go into the 100mm extraction piping.

Working out the logic of each relay bank was cool. Got that sussed. Working out the cheapest and easiest way to prove a machine has been switched on has worked. The pneumatic solenoid bank works.

I am an engineer not an electronics engineer but learning. Please bear with me I am learning how to write proper schematics but not being able to access the proper component symbols on Visio is a toughy. Its a legit program but given to me and I stopped it from accessing the internet in case all the licenses have been used!

Happy faces.

 

[davenn]

In the diagram, there is a fourth 12vdc power-supply which will run across the relay contacts, also that fourth 12vdc will run to the secondary relay bank(not shown). But will be separate from the other relay contacts hence the diode. I have only shown one. Each relay will have an additional output.

Make sense?

not completely

OK on the relay contacts ... it would have been real easy to get an image off the net

BUT your circuit DOES NOT show 12V power to all the relay contacts
you really should redraw the circuit

this is where confusion reigns and those trying to help you play 20 questions trying to figure out what you are trying to achieve


Dave

 

[boyd]

Hi Dave. Thanks and sorry. I will do just that and even take a Picture!