Valhalla 2703/2705 - need both units?...  - Page 1
Forum section: electronics / general

author: Rax
author_rank: Super Contributor
timestamp: August 04, 2023, 04:00:26 pm
content: I may have an opportunity to grab a 2705, but even after roughly going through the manual I am unsure how these two modules (?) hookup and provide full functionality.Can the 2705 be used by itself as an AC standard?Interestingly, there's another thread on the 2703 right now... I didn't think these units are so ubiquitous. But maybe that offers an opportunity to discuss this pair a little more thoroughly.Thanks!

author: alm
author_rank: Super Contributor
timestamp: August 04, 2023, 06:46:58 pm
content: I don't think the Valhalla 2705 can be used by itself as is. It lacks the circuit to generate the the frequency signal on its own. You might either be able to deduce from themanualhow to drive it. Page 8-6 gives a rough overview of the signals that are necessary. Looks like some clock signals and a bunch of digital signals.For stand-alone operation I'd think you'd have to design a replacement for the frequency board (drawings 2703-072, 2703-603 and 2703-073) instead of the phase generator board (dwg 2705-074). I don't know if these boards are similar. I've never seen a 2705 in real life, although I do have a working Valhalla 2703. I believe the 2703 firmware is already available. If you're very lucky, the 2705 board might be the same PCB with different stuffing, but I wouldn't count on that.

author: Rax
author_rank: Super Contributor
timestamp: August 04, 2023, 07:51:10 pm
content: Quote from: alm on August 04, 2023, 06:46:58 pmI infer from this that the 2703 can work standalone?...Thank you very much, alm, for the detailed information on the boards and potential path forward.Is my initial understanding of these units correct? Which is that they are supposed to work as a pair. But maybe not at all, as I'm seeing the 2705 positioned as a "slave" while the 2703 is always a "master." How they work together (or separately, for that matter) still being a mystery to me.

author: alm
author_rank: Super Contributor
timestamp: August 04, 2023, 08:13:43 pm
content: Yes, the 2703 is designed for stand-alone operation or as a "master". I've only used it stand-alone since I don't own a 2705. The 2705 can only be "slave" to a 2703. The 2703 will produce a single phase, and you can optionally add one or two 2705s to gain additional signals with the same frequency but a phase shift relative to the 2703. You might use this to simulate a three phase voltage source, for example. Valhalla also made three phase power meters. So I'd say the 2705 is more much niche than the 2703 unless it could be made to work standalone. The 2703 can not be a "slave" to another 2703. It misses the "to master" cable connector. Seehere. On page 8-2 of the manual is a diagram of how a 2703 and one or two 2705 are to be connected.The 2703 generates a clock signal at the desired frequency, and the 2705 follows this frequency but introduces a phase shift. So it might be 120 degrees behind the 2703. It's described in the theory of operations in the 2705 part of the manual.

author: Rax
author_rank: Super Contributor
timestamp: August 05, 2023, 11:30:55 pm
content: Quote from: alm on August 04, 2023, 08:13:43 pmThat is very helpful, thank you very much, alm.