Thursday, March 4, 2010

Chapter 4 - Exercise 20 Update

After searching (calling, actually) everywhere in Atlanta, it appears that no one (Radio Shack or ACK Supply) seems to carry the DPDT dual coil latching relay. Argh.

So, I've ordered it from Mouser. But I've got a gripe with Mouser... they do not provide a shipping price until they've actually shipped the order. So I have no real way of knowing what UPS ground is going to cost except for their rough estimate. I'm sure that estimate will be close, but it would be nice to have an actual shipping cost as part of the order before clicking the Submit button. Oh, well.

I've got to solder up that wire ribbon to the numeric keypad today... should take some time as the wires are very tiny and easy to tear.


  1. Mouser has an unbroken record, in my experience, of charging very low shipping fees, but it may depend on where you live. In Calif I think you will pay sales tax, which is annoying.

    Latching relays are available from all the big supply houses, such as Digikey and Newark, and of course never forget eBay! I just saw a couple of latching relays on eBay for $1.29 each. But they are not a Radio Shack item.

    Their advantage of course is that you just send a pulse, and the relay stays there without eating any additional power. For the project you're working on now, James, this is relevant, because my suggested application could require the relay to stay closed for hours or even days.

    You can get solid-state relays which consume very little power in either "on" or "off" state but I decided not to get into them for this book.

  2. Thanks, Charles... I ordered one originally from Mouser back when I did the bulk Shopping List but it doesn't seem to work... so that's why I'm having to purchase an extra one.

    And by the way, congrats on the parts packs from MakerSHED... that should benefit existing owners and readers as well as encourage new sales of the book.

  3. Have you tried Electronics Goldmine? My son seems to find more parts there than anywhere else.

  4. Thanks, Julie... haven't ever heard of EG, but I'll definitely add them to my list of sites when pricing out items.