not enough current for relays?

[Boyan Silyavski]

Hi,
how do i deal when a board / Pokeys57CNC does not output enough current on output 5v pins to switch a external relay / 8 channel relay board 5vdc /??

Leds light but not bright enough and no switching happens.

Do i buy their relay board which has other type of communication with the BOB or there is sth i can do to make the general Chinese relay board work

their board is 30eur versus 10 euro for general low high chinese relay board. and i need 2 .

[Clive S]

Boyan You don't say how you are powering the Pokeys board.
This is from the manual:-

[PoKeys57CNC requires external 6-26V power supply to be connected to the board in order for the device to operate correctly (device may not operate according to the specifications if the external power supply is not present). The device uses switching power converter to scale down the input power supply to 5V. The power supply should be capable of providing at least 2.5W.]

[Boyan Silyavski]

24vdc 150W, but it seems its irrelevant for the outputs


seems it was never meant to do that, look bellow at specs from pdf. I wonder why sb will do such nice board, but that could not power an input of a bloody relay


http://www.mycncuk.com/attachment.php?attachmentid=15872&stc=1

[Boyan Silyavski]

so what you say Clive, i buy their relay board? and forget about the case

[Boyan Silyavski]

ok, i sorted it out.

it seems they have another product PoExtBusOC16 , which - incorporates 16 high current/voltage open collector outputs which suits applications such as lamps, relays.

[Clive S]

24vdc 150W, but it seems its irrelevant for the outputs


seems it was never meant to do that, look bellow at specs from pdf. I wonder why sb will do such nice board, but that could not power an input of a bloody relay


http://www.mycncuk.com/attachment.php?attachmentid=15872&stc=1I read that Boyan but it seem to indicate you can take out the 100R and then get 50mA what do you think. ..Clive

[Boyan Silyavski]

i read somewhere that the relays need more than that, ~80-100mA so at the end i bought the extra boards.

i wish sb simplified the stuff and said- " you need that board and that relay board or output board, cause otherwise you will not be able to do this and that " cause for me 50mA is like chinese.

how difficult would be to do that if you sell a product

[Clive S]

i read somewhere that the relays need more than that, ~80-100mA so at the end i bought the extra boards.

i wish sb simplified the stuff and said- " you need that board and that relay board or output board, cause otherwise you will not be able to do this and that " cause for me 50mA is like chinese.

how difficult would be to do that if you sell a productI think a lot of small relays will switch at about 15mA https://www.sparkfun.com/products/100 or even less

[Boyan Silyavski]

Did not think of switching them directly.

Now i read that the relays i was going to use are triggered only by 5mA, so why would they not work?

By the way it looks a really quality stuff. and has LOW HIGH jumperson each pin. I have used it before with great success


Module Description :
1, the module uses genuine quality relay , normally open interfaces Maximum load : AC 250V/10A, DC 30V/10A;
2, using SMD optocoupler isolation , driving ability , stable performance ; trigger current 5mA;
3, the module voltage : 5V
4 , each way module can be set high or low triggered by jumper ;
5 , fault-tolerant design , even if the control line is broken , the relay will not operate ;
6 , the power indicator ( green ) , 8 relay status indicator ( red )
7 , interface design humane, all interfaces can be connected directly via terminal wiring leads , very convenient
8 , Module size : 141.5mm * 50mm * 18.5mm ( L * W * H )
9 , has four mounting bolts holes , hole 3.1mm, pitch 136mm * 44.5mm

http://www.mycncuk.com/attachment.php?attachmentid=15873&stc=1

[Clive S]

Did not think of switching them directly.

Now i read that the relays i was going to use are triggered only by 5mA, so why would they not work? You would have to show how you are connecting them . It could be a problem in the way you are grounding them.

[HankMcSpank]

I have one of those relay boards (or at least one that looks remarkably like it) - I drive it directly with the 5V out from a CNCUSB Mk2/9 board digital output - no issues.

I'd measure the DC resistance of your relay coil...I'd wager you can probably short out that output 100 Ohm resistor (which should then see sufficient current to energize the relay) ...else play on the safe side & put something like a 10 ohm resistor across it (i.e. in parallel with it)

[cropwell]

You may have a faulty board. Try hooking it up to a 5v power supply and see if you get a relay operating with 5v from the same supply. Some boards I have switch the relay on with 0v and off with 5v. Also check the jumpers.

[HankMcSpank]

Actually ignore my last post...if your relay board is the same as mine, from recollection the 5V from your driving IO pin, doesn't energize the relay directly, but does so via a tranny/fet. Are you supplying the relay board with a separate 5V supply?

[Boyan Silyavski]

Actually ignore my last post...if your relay board is the same as mine, from recollection the 5V from your driving IO pin, doesn't energize the relay directly, but does so via a tranny/fet. Are you supplying the relay board with a separate 5V supply?

BOB is supplied with 24v, relay board with 5v. I use different supplies for galvanic isolation of BOB, sensors,etc.

[Clive S]

BOB is supplied with 24v, relay board with 5v. I use different supplies for galvanic isolation of BOB, sensors,etc.
Boyan Can you show just how you are connecting the relay to the board you might have to connect the -ve grounds to each other.

[HankMcSpank]

Boyan Can you show just how you are connecting the relay to the board you might have to connect the -ve grounds to each other.

He will definitely need to connect the two boards PSU 0V rails together, else all he'll have is two independent supplies with their respective 0Vs floating wrt one another. As mentioned in my last post, my relay board uses a FET/tranny on the input ...the switching/control voltage does not drive the relay coil direct. Therefore if your board is like mine, the notion that the "Pokeys57CNC does not output enough current on output 5v pins to switch a external relay" a misnomer (the input impedance of the relay board will likely be extremely high so will sink very little current at all)

[Boyan Silyavski]

Guys, so i have BOB powered by separate 24VDC PSU and relay board powered by 5VDC PSU. Both grounds are connected/the earth, the body.

So you say now i need to connect the together the 2 - /minus / pins of both the PSUs?

Makes sense though i have never done that before on other boards and they worked

[HankMcSpank]

Without a diagram of your particular situation, all we have to go on is this....


Hi, how do i deal when a board / Pokeys57CNC does not output enough current on output 5v pins to switch a external relay / 8 channel relay board 5vdc /??


If you get a multi-meter & see what the resistance is between the Pokeys57CNC 0V rail & the relay board's 0V rail ....if it's high resistance , then there's no common path (& therefore this is why your relay's aren't switching).... you will need to link the 0Vs on both boards together. Voltage is always 'with reference to another point' ...i.e. the 5V on your Pokeys57CNC is in reference to the Pokeys57CNC 0V, the 5V on your relay board is in reference to your relay board's 0V...the only way you can make the 5V on your Pokeys57CNC mean anything to your relay board is to commonize the 0V rails on both boards....join them together.