I had this same issue when I worked through Make: Electronics -- sometimes, no matter how hard you look, you just can't find a component when you need it. I'm not talking about waiting for shipping... I'm talking about a part completely out of stock and on back-order. (See image -- Amazon has them, but $10 for part and $10 for shipping? No thanks.)
That's the situation I'm facing for Experiment 7 -- this 3VDC latching relay is becoming a real problem. I have a 5VDC, but the book is pretty clear that the voltage of the circuit won't be enough to ensure the 5VDC relay works properly. I've ordered the relay from Mouser, but it's on back order and not expected to ship until September. Yeah, September.
My local supplier (ACK) doesn't have them, and I couldn't find it on a few other parts suppliers' websites. It's a very specific component (Panasonic) and although I'm certain there are latching relays out there that could be used as a substitute, these things are NOT cheap. I'd really rather not spend $7 or $10 on a specialty relay (plus shipping costs) to discover it's not a good match.
I'm going to use this post as a placeholder for Experiment 7 -- it's going to be empty. Don't let that bother you. It's just so I can try and keep the experiments in a somewhat logical order for anyone finding this blog at a later time. The plan is to come back and finish Experiment 7 and document it here by updating this post. I'm fortunate that I already have all the components I need to finish Experiments 8 to 15, so rather than stop and wait for the latching relay, I'm going to plow forward with Experiment 8. My apologies, but as soon as that relay arrives I'll circle back and update this post.