Dont own a load - Page 1
Forum section: electronics / beginners

author: Mp3
author_rank: Frequent Contributor
timestamp: May 08, 2020, 09:18:23 pm
content: I got my 1st REAL bench power supply, a nice 3 channel unit, which is very exciting to have instead of using a handful of $10 boost converters hooked up to DC wall warts. And then i started reading the manual for the power supply i realized i don't have a load to hook it up to.I see a variety of wirewound resistors sold as loads to up to 200W or so, should i get a couple of those and put them on the power supply's terminals when the manual instructs me to attach it to a load?? My understanding is that whatever would work as a "bleeder resistor" on something like a charged capacitor is suitable here.Thanks in advance. For the record it can do up to 5a of 5v and up to 1a of 0-36v, so according to my calculations, i would probably be safe to use a 1 ohm on the 5v/5a and maybe a 10 ohm on the 0-36v/1a, to keep the load under several hundred watts.https://www.ebay.com/itm/300W-5-Ohm-Power-Resistor-Wirewound-Aluminum-Load-w-screw-nut/382572787139

author: The Soulman
author_rank: Super Contributor
timestamp: May 08, 2020, 09:22:51 pm
content: What are trying to accomplish here?Just to see if the power supply is properly working?

author: Manul
author_rank: Super Contributor
timestamp: May 08, 2020, 09:25:37 pm
content: And what is idea? You want to heat house?

author: Mp3
author_rank: Frequent Contributor
timestamp: May 08, 2020, 09:27:47 pm
content: Quote from: The Soulman on May 08, 2020, 09:22:51 pmYes, sorry. The preliminary setup section of the power supply says to test it with a load, so I thought I should probably own some load resistors, since I would like to have them if i need them, but definitely i don't have a need for something fancy like an Agilent.I don't actually have any use case i can imagine for a 50w+ resistor besides testing my power supply.

author: Manul
author_rank: Super Contributor
timestamp: May 08, 2020, 09:33:52 pm
content: I do not see reason to test bench supply. If it will fail, you will notice. Until then just use it, it is made to have these specs and it probably does. Load testing is needed when you build a power supply yourself and want to characterize it. Bench power supply is already characterized by manufacturer, so just trust it.

author: KingSolomon
author_rank: Contributor
timestamp: May 08, 2020, 09:37:44 pm
content: You could also build a simple load yourself as outlined in EEVblog #102.

author: Picuino
author_rank: Super Contributor
timestamp: May 08, 2020, 09:56:23 pm
content: You can use a simple car light bulb of 21W (voltage max = 12 volts) or a combination of several ones.They are robust, very cheap and do not need a heat sink.

author: wizard69
author_rank: Super Contributor
timestamp: May 08, 2020, 10:39:18 pm
content: I wouldn’t worry too much about this, I suspect the manufacture just wants you to power something up with it.Given that it doesn’t hurt to have a few power resistors laying about. This especially if you want to work with audio circuits. So 4, 8 and large resistors I the 20 watt range can be handy to have. Series and paralllel connect them to get the resistance value you need.Basically a parts box without a few power resistors is incomplete. However you don’t need specialized components to test a power supply. I’ve even have used steel banding from a shipping crate for an impromptu load.

author: Rick Law
author_rank: Super Contributor
timestamp: May 09, 2020, 01:05:17 am
content: Quote from: Picuino on May 08, 2020, 09:56:23 pm++ on car light bulbsI do have an adjustable load ~1.5A max. For larger loads, the car bulbs are my "go to" solutions.You can have some control of total load by how many bulbs you parallel (and/or serial). My favorite is the dual-filament (brake and parking light). With the dual-filament, you have 2 bulbs in one giving you more mix.By the way, two additional notes:(1) While they don't need heat sink, they do get very hot. So do be careful to avoid getting burn.(2) Their current draw changes quite a bit - between cold start up and after they get full brightness. You can exploit this property, or just make sure you don't let that change mess you up.

author: Gyro
author_rank: Super Contributor
timestamp: May 09, 2020, 09:19:52 am
content: Old school (literally in many cases) vintage rheostats make excellent dummy loads. The long tubular ones with a linear slider. There seem to be as many ebay listings for them in the US as there are in the UK.I have a 3.3R @ 10A (that's 330W at 33V!), a 15R @ 4A and a 135R @ 1.4A, which cover all of my load needs. The tubular cores that they are wound on are enamelled steel, which keeps their inductance fairly low (shorted turn effect). They also usually have 4mm binding posts or terminals.Avoid the commonly available rotary wirewound ones if possible. They tend to be rated for wattage (whole element) rather than current, and the wipers can typically handle much less current than the wattage rating suggests.

author: Jwillis
author_rank: Super Contributor
timestamp: May 09, 2020, 10:00:44 am
content: One option for you is to pick up one of those 150W or 180W constant current loads from Ebay for around 40 bucks. They can handle quite a bit on their own . More than enough for a 25 to 36 watt power supply. I have two of them. One is attached to 6 parallel FDL100N50F power MOSFETS . The other I up graded by removing the original IRFP260N and putting the FDL100N50 and a 6 pipe CPU cooler. Just enough room for the new MOSFET. Testing with a clamp meter they turned out fairly accurate.You can get the MOSFETs fairly cheap right in the U.S. if you feel like upgrading .