Stahl Control Unit with diode

[RJJ]

Hi everyone, I recently came across this particular product installed inside an enclosure (https://r-stahl.com/en/global/produ...s/control-devices/resistor-series-8453-49633/). The one that I saw has a 1N4005 diode fitted inside of it and is used as a blocking diode to prevent current backflow (24VDC circuit). After being installed, the unit with diode works for a while and prevents current backflow as intended. But after some time, it shorts out and does not block the backflow.

I was initially thinking that it could be that the 1N4005 is a 1A diode and that maybe a higher current could have flown through it leading it to failure. However, I am not sure if this the reason. Stahl makes a similar unit with a SB550 diode inside, which is a 5A diode. Do you think that would help? Any thoughts?

-RJ

 

[gar]

181115-1663 EST

Very incomplete information. Provide a circuit diagram.

What do you mean by back flow? From where? Is a relay being switched? If so, then a series diode is probably the wrong approach. In the case of a relay or other inductive load it is likely a reverse biased diode would be shunted across the relay coil. On turn off this causes the inductive stored energy to be dissopated in the relay coil. Opening an inductive circuit with current flowing causes a very large induced voltage to be produced across the inductor.

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[LarryFine]

I would try the 5a diode after measuring the forward (normal) current, making sure it's at least 100v (piv). The 1N4005 voltage rating is more than you need, and shouldn't be an issue.

1N4001 = 50v, 1N4002 = 100v, 1N4003 = 200v, 1N4004 = 400v, 1N4005 = 600v (if memory serves).

 

[RJJ]

181115-1663 EST

Very incomplete information. Provide a circuit diagram.

What do you mean by back flow? From where? Is a relay being switched? If so, then a series diode is probably the wrong approach. In the case of a relay or other inductive load it is likely a reverse biased diode would be shunted across the relay coil. On turn off this causes the inductive stored energy to be dissopated in the relay coil. Opening an inductive circuit with current flowing causes a very large induced voltage to be produced across the inductor.

.

Sorry for not being complete in my information.
So this diode approach is basically to solve a design error. There was current flowing unintentionally from a different enclosure into some terminal blocks in this one. This particular diode was installed in this enclosure to prevent (blocking) that from happening. I hope that makes sense.

 

[RJJ]

I would try the 5a diode after measuring the forward (normal) current, making sure it's at least 100v (piv). The 1N4005 voltage rating is more than you need, and shouldn't be an issue.

1N4001 = 50v, 1N4002 = 100v, 1N4003 = 200v, 1N4004 = 400v, 1N4005 = 600v (if memory serves).

Can you tell me what you mean the word "PIV"?
I agree the voltage rating is def not an issue since these are being installed on a 24VDC circuit.

 

[gar]

181116-1057 EST

PIV is peak inverse voltage.

I can produce thousands of volts from a low voltage. A 12 V battery, switch, and inductor. Think about an automotive ignition system.

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