Big daddy electronic load - Page 1
Forum section: electronics / projects

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 01, 2018, 12:39:27 am
content: 500V 4A capacity. Load resistors not shown. Uses resistors to save money on heatsinks and improve reliability. Sure is nice needing only half as many transistors, and seven times less heatsinking, than a 100% linear version!The right side of the main board is made so that it can be left in place and wired with ribbons, or detached and stacked as shown.Tim

author: CopperCone
author_rank: Super Contributor
timestamp: May 01, 2018, 01:20:40 am
content: how does frequency response on something like that look like? for pulsed loads

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 01, 2018, 01:25:05 am
content: Targetting audio range (by coincidence, not intent).Tim

author: larsdenmark
author_rank: Regular Contributor
timestamp: May 01, 2018, 08:38:04 am
content: Don't you still need a large heat sink and a big fan if you are going to dissipate 2000 W?

author: Blinkenlights
author_rank: Contributor
timestamp: May 02, 2018, 06:11:40 am
content: Quote from: larsdenmark on May 01, 2018, 08:38:04 amI think that is what the OP is saying -His design does not need AS MUCH metal, as resistors can be run a lot hotter than Silicon.

author: RobertHolcombe
author_rank: Frequent Contributor
timestamp: May 02, 2018, 06:30:12 am
content: This thread reminded me of mike's video

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 02, 2018, 03:04:49 pm
content: Quote from: Blinkenlights on May 02, 2018, 06:11:40 amYup, less surface area is required. So it can be smaller too! Just mind the exhaust temperature...Tim

author: nctnico
author_rank: Super Contributor
timestamp: May 02, 2018, 05:08:19 pm
content: Don't forget to add overvoltage clamping if you are switching the resistors using a MOSFET. The self inductance can be enough to kick a nasty spike back.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 02, 2018, 08:45:50 pm
content: Yup, they're slowed down adequately.Also a fuse, current limiting resistor and MOVs on the load side, to protect against overvoltage.Tim

author: rmacintosh
author_rank: Regular Contributor
timestamp: May 02, 2018, 10:12:51 pm
content: Any more details you can share on the design?Or is this not a hobby project

author: fourtytwo42
author_rank: Super Contributor
timestamp: May 04, 2018, 07:59:19 pm
content: Looks a lot prettier than my assorted combinations of electric fires and kettles, thermostats cutting out unexpectedly can also cause momentary terrifying experiences and sometimes bad smells

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 19, 2018, 02:07:04 pm
content: I do love how fast PCBs arrive from literally the other side of the world.Now it's all up to mechanicals, like deciding which heat sink to use. Hmm.Regarding details, I haven't decided yet if this should be a product, or just a project. Either way, your interest is appreciatedTim

author: fourtytwo42
author_rank: Super Contributor
timestamp: May 19, 2018, 07:31:04 pm
content: Neat soldering job TimIs that auto-fusing power resistors I see (soldered on lead extension)

author: schmitt trigger
author_rank: Super Contributor
timestamp: May 19, 2018, 07:37:11 pm
content: Impressive!What CAD program did you use to generate the PWB artwork?

author: Bud
author_rank: Super Contributor
timestamp: May 19, 2018, 08:40:32 pm
content: Tim not sure if this because of the photo but the controls seem crowded. I am trying to picture how it would look on the front panel if put in the enclosure.

author: ocset
author_rank: Super Contributor
timestamp: May 19, 2018, 09:47:07 pm
content: Looks good to me.I would certainly like one.I like the idea of having the significant resistor content. Pure linear regulator based E loads are not as good in my opinion. I remember testing an SMPS with minimal output capacitance into an E load that was pure linear regulator based. A lot of the ripple current from the smps output was going into the E load. –This wasn’t the case when I loaded the smps with an equivalent power resistor. It shows that pure linear regulator E loads look to an extent capacitive. That’s not always good for smps testing, because as you know, the output capacitance is a smps feedback loop parameter, so , in some cases, the last thing you want is an E load that has significant capacitance property…especially if youre doing transient response testing….where the dynamics of the smps is important, and you don’t want to be adding extra “capacitance” to the output…because that in itself will affect the transient response.

author: Jester
author_rank: Frequent Contributor
timestamp: May 20, 2018, 12:24:33 am
content: More details please, looks like a better option than my bunch of paralleled light bulbs and 100W variable power resistor that I use for ac load testing.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 20, 2018, 12:46:10 am
content: Quote from: fourtytwo42 on May 19, 2018, 07:31:04 pmTrick to SMTs is -- aside from using paste and reflow like a good assembler would-- blob solder on a few pads, tack the part in place, go around and do the other pins, then, settle the part in place with a hot air machine (and waving the air back and forth, or jiggling the board, or bumping the parts with tweezers). And yes, I realize with hot air, I can paste and reflow, I just haven't gotten around to getting paste (and masks where applicable) yet.Controls are crowded, yes; I wanted to keep the stacker board small. Intent is to put some display or interface of some sort on top of it (via the two smallish headers), preferably an SPI LCD, and isolated RS-232 interface. (Isolated because everything is common ground, so if you're testing a negative supply...)Design is Altium, of course.Tim