Test Equipment required - Page 1
Forum section: electronics / testgear

author: jwhitmore
author_rank: Regular Contributor
timestamp: April 24, 2015, 10:09:31 am
content: I should maybe start my first post here by stating that I'm SW Engineer let loose with soldering Iron.I'm trying to test a product I'm designing but need a few bits and pieces to do so. Not sure what is the best way to do this testing but I'll try to explain what I have to test.My product has a Switched Mode Power Supply built around the LTC3606  Chip. That chip is rated at 15V / 2.5 Amps but my bench top power supply will only supply 1.1 Amps so have to upgrade that for a start.The product has a USB Host mode so I'd like to somehow load that USB power connection with 500mA. There's a PTC Fuse  in the USB power feed so I'd like to test that by pulling current over the 500mA till it cuts out the circuit. Just to make sure it works. (I'm confused by all the current numbers listed for PTC devices). The USB host will only support one device so limited to 500mA max.Apart from the USB Host mode connection the board has a microcontroller and various expansion options. I'd like to make sure that the DC-DC can generate the 5V within USB Specs (4.75 - 5.25 is acceptable) and supply at lease 2 Amps over some range of DC Input voltage say 7V - 15VWhat I've got at present is limited to a USB Scope and a multimeter. (I discovered EEVblog far too late in life :-) The multimeter does have a current meter but it's one where you feed a wire through a loop in the meter, not sure how accurate it is.So for a start I'm going to need a bench top power supply which can supply maybe 3Amps, some way of loading the circuits, without going on fire, and an accurate way of measuring current.Did I mention I'm on a bit of a shoestring? Thanks for any assistance you can offer. Having discovered EEVblog I have a lot of catching up on videos to do. :-D I did see a video that recommended a Hakko FX888 I think it was. Went looking for it but obviously it's been superseded.http://uk.farnell.com/linear-technology/ltc3603imse-pbf/buck-synch-2-5a-12v-16msop/dp/2295093http://uk.farnell.com/multicomp/mc33189/fuse-ptc-reset-smd-60v-300ma/dp/1800748jwhitmore

author: KJDS
author_rank: Super Contributor
timestamp: April 24, 2015, 11:12:29 am
content: For the power supply, so long as you don't mind some fan noise, you could use a HP6632A or B.These will supply up to 20V at up to 5A and the meters are accurate. Buy two and you have the advantage that you can use one as a load, set the voltage to 0 and the current to the amount you want to draw and it will sink the set current.

author: PA0PBZ
author_rank: Super Contributor
timestamp: April 24, 2015, 11:28:04 am
content: Have a look at this:https://www.eevblog.com/forum/buysellwanted/fs-(uk)-hameg-hm8143-3-channel-arbitrary-psu-and-electronic-load-41381/

author: McBryce
author_rank: Super Contributor
timestamp: April 24, 2015, 11:29:53 am
content: Quote from: jwhitmore on April 24, 2015, 10:09:31 amHi J,you're confusing things a bit here. The LTC3606 rating of 2.5A means that it can theoretically supply that much current, but it will still only require/supply what your device needs. So to begin with, your 1.1A supply is fine for powering this up unless your bare device is pulling >1.1A (which seems a lot). Obviously if you are load testing your device with lots of options (up to 2A you say), then a bigger supply would be required.With all that said. What exactly is this device? The current consumption figures seem very high for a modern USB device unless it's charging lots of USB devices or something similar.McBryce.

author: new299
author_rank: Regular Contributor
timestamp: April 24, 2015, 12:34:05 pm
content: Quote from: jwhitmore on April 24, 2015, 10:09:31 amI'm also a SW engineer with a soldering iron I guess. But... if you're on a shoe string you might want to stick with the supply you have. Then buy whatever fixed voltage supply you plan to use for the final product for testing at higher currents.Quote from: jwhitmore on April 24, 2015, 10:09:31 amI'd spend the money on a standalone scope (the new rigol seems good) and a decent multimeter (there's a big review thread, and several videos here).Quote from: jwhitmore on April 24, 2015, 10:09:31 amThe fx888 was replaced with the fx888d. The old one had an analog input, the new one digital. I don't like the UI on the digital one much to be honest. The Aoyue 936 are clones of the Hakko stuff and use the same tips. They're pretty good and only about 40GBP.

author: jwhitmore
author_rank: Regular Contributor
timestamp: April 24, 2015, 10:19:55 pm
content: Thanks a million for all that food for thought. The HP6632 looks magic as does the HAMEG 8143. That link to another posting on here was great value but already sold. I've got a much better idea what I'm looking for and given the price for the HAMEG 8143 of 1,250 yoyos I'd have to talk to the bank ;-)I agree that the current demand I'm looking at is a bit high. But of the many USB devices that can connect to a host connection one is an Android phone. It'll attempt to charge the phone from the connection so will potentially pull the max 500mA on USB2.0. I did have a 7805 in a prototype design and man did that get hot.Apart from that 500mA the board has a microcontroller and I/O headers for development work.