. .
Page 2 of 4 FirstFirst 1234 LastLast
  1. #11
    dsc's Avatar
    Lives in Lincoln, United Kingdom. Last Activity: 17-06-2020 Has been a member for 9-10 years. Has a total post count of 252. Received thanks 1 times, giving thanks to others 11 times.
    Just a quick update, I've tried both the resistor and the diode, both get rather hot, although the diode seems to handle it better. Done some checks with a TC and the resistor sits at around 80degC whereas the diode goes up to around 60deg. The ideal solution would be to change the PSU to a 48VDC, but with the current solution costing less than a pound I don't think I'll bother:)

    T.

  2. Did you mount diode on a bit of board as I suggested? It's running a little hotter than I calculated. Junction temperature will be around 120 degC, still less than the maximum allowed of 150 degC, but 20 degC more than I'd like.
    Last edited by irving2008; 13-10-2014 at 05:50 AM.

  3. #13
    Hi you say your wanting to connect a LED to a 68VDC PSU. you can use a LED with a resistor in series If your machine is on permanently, I would suggest to drop the current to 15mA, LEDs work at 20mA but run constant shortens their life expectancy. If your LED is a 24 volt version check the spec on it the resistor already in situ may already drop the current to the LED to 12~15mA, just remember the power supply you are connecting to will either be PWM or linear my guess PWM either way the voltage (68VDC) will be constant

  4. #14
    dsc's Avatar
    Lives in Lincoln, United Kingdom. Last Activity: 17-06-2020 Has been a member for 9-10 years. Has a total post count of 252. Received thanks 1 times, giving thanks to others 11 times.
    This was only a quick test with a choc block, I'll need to cut up a piece of laminate and give it another go.

    T.

  5. #15
    Hi, you should not need a diode your power supply will be polarized +ve & -ve your problem is you are trying to drop 44 volts which creates a lot of heat, if your voltage was a bit lower you could have used a LM317 or similar the best you could input to these would be 32vdc its a weird voltage drop to are trying to use my suggestion is to try to get hold of a NUD4011 http://www.onsemi.com/pub_link/Collateral/NUD4011-D.PDF
    this should handle your voltage drop

  6. #16
    Quote Originally Posted by Binary View Post
    Hi, you should not need a diode your power supply will be polarized +ve & -ve your problem is you are trying to drop 44 volts which creates a lot of heat, if your voltage was a bit lower you could have used a LM317 or similar the best you could input to these would be 32vdc its a weird voltage drop to are trying to use my suggestion is to try to get hold of a NUD4011 http://www.onsemi.com/pub_link/Collateral/NUD4011-D.PDF
    this should handle your voltage drop
    Hi and welcome to the forum. Have you read this complete thread because I think you have missed the point and purpose about the diode also all the math has been done. I am not trying to put you down in any way but this guy has stated he wants a simple way and he is short of space ..Clive

  7. #17
    Thank you for the welcome. I understand he has a problem with space but if you are using a 5Watt resistor you need a lot of space the chip i suggested can be mounted on a 15mm x 8mm pcb depends how you proceed, that would include a smd resistor also i use its brother the nud4001 so i know how small it is, the chip is a current limiting chip that is why it can be used with such high voltages up to 200Volts input as for the price i pay around 30p for the nud4001 the price for the nud4011 is a little higher..its only a suggestion he does not have to use it but many brains make light work lol i'm not sure it may even fit on the pads of a piece of vero board,
    One other point " a LED is a Diode" a zener can be used to "clamp" the voltage" you just need to current limit it, I also have another chip in mind and the size of that is only 3mm looks like a smd diode 2 pins thank you clive

  8. #18
    dsc's Avatar
    Lives in Lincoln, United Kingdom. Last Activity: 17-06-2020 Has been a member for 9-10 years. Has a total post count of 252. Received thanks 1 times, giving thanks to others 11 times.
    I've made a small PCB 62mm x 40mm, it's got a larger section of copper on the banded area, roughly 38mm x 40mm. Just ran some tests and it levels at around 56degC, so better than before, but not massively.

    I do like the NUD chip, the issue is it's SMD (can't solder those) and for 68VDC and a single LED it's over it's power limit anyway. I guess I might have to get that 48W PSU anyway...

    Cheers,
    T.

    BTW. I'm not limited for space, I've got loads:)

  9. #19
    Quote Originally Posted by dsc View Post
    I've made a small PCB 62mm x 40mm, it's got a larger section of copper on the banded area, roughly 38mm x 40mm. Just ran some tests and it levels at around 56degC, so better than before, but not massively.

    I do like the NUD chip, the issue is it's SMD (can't solder those) and for 68VDC and a single LED it's over it's power limit anyway. I guess I might have to get that 48W PSU anyway...

    Cheers,
    T.

    BTW. I'm not limited for space, I've got loads:)
    This is what you quoted [Those 7seg displays are pretty neat considering the voltage range on them. I'll have to stick with a small LED indicator as I'm tight on space as it is.] This is why I mentioned that ..Clive

  10. #20
    dsc's Avatar
    Lives in Lincoln, United Kingdom. Last Activity: 17-06-2020 Has been a member for 9-10 years. Has a total post count of 252. Received thanks 1 times, giving thanks to others 11 times.
    Should've been more clear, I've got no space on the front panel, but loads in the guts, which basically means I need to stick with a single panel mounted LED and whatever internals it needs.

    T.

Page 2 of 4 FirstFirst 1234 LastLast

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. RFQ: Daft Punk Build
    By FIREWIRE in forum Projects, Jobs & Requests
    Replies: 0
    Last Post: 19-04-2013, 02:34 AM
  2. I promise I will stop asking daft question soon. Ish.
    By D.C. in forum Gantry/Router Machines & Building
    Replies: 27
    Last Post: 15-10-2012, 11:37 PM
  3. A daft question about vibration damping
    By D.C. in forum Gantry/Router Machines & Building
    Replies: 11
    Last Post: 11-10-2012, 09:57 AM
  4. NEW MEMBER: Hi there, a new member from Mid-Wales with a couple of daft questions.
    By m0nk3hjam in forum New Member Introductions
    Replies: 6
    Last Post: 17-08-2010, 02:32 AM
  5. High speed spindle
    By leadinglights in forum Tool & Tooling Technology
    Replies: 0
    Last Post: 27-04-2010, 09:23 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •