Yeah for a hundred watts max each. So, you want to parallel 20 of them and ballast them to force current sharing? Plus burn up all the heat in the transistor and heat sinks rather than a resistive load?
Would not be my first choice. From: David via Af Sent: Friday, January 02, 2015 10:03 AM To: [email protected] Subject: Re: [AFMUG] Dc electric load ? Chuck ? Good ol 3055 transistor found and Astron and Duracomm systems. Use a LM723 and a few other components. The one in question would be the output resistor at 5W .33Ohm I have built several of these to regulate 12-18vs seamlessly to our mikrotik routers to help with smoothing out the raw dc from the duracomm systems at 24v-48v out. Our mikrotiks seem to have fewer issues related to power and reboots. Went the whole last year without a single reboot on the network. On 12/31/2014 04:59 PM, Forrest Christian (List Account) via Af wrote: The electronic way is a constant current source shunted to ground or through a resistor bank. One hefty npn power transistor and a few smallish components. Or a jfet with source tied to gate, with a current adjustment resistor in the source lead. Or any of a hundred circuits. For more wattage you can parallel several, each adjusted to take their fraction of the total amps. I seem to be slowly turning into a power electronics engineer over here. On Dec 31, 2014 3:42 PM, "chuck--- via Af" <[email protected]> wrote: I am thinking a DC-DC converter that will take a wide input and constant voltage output into a nice temperature compensated resistive load. What voltage range do you want? Doh!, that would be a constant power load. You want constant current load. Have to continue thinking... From: [email protected] Sent: Wednesday, December 31, 2014 3:39 PM To: [email protected] Subject: Re: [AFMUG] Dc electric load ? Chuck ? I know how to do it really cheap and easy under 2 amps. Have to think on this a bit. I have used hot water heating elements and coils of wire (in a bucket of water) for high wattage resistors but obviously not constant current. From: TJ Trout via Af Sent: Wednesday, December 31, 2014 12:11 PM To: [email protected] Subject: [AFMUG] Dc electric load ? Chuck ? Anyone know of a inexpensive do it yourself way to make a dc constant current electric load for testing power supplies, lithium batteries , etc ? Looking for something maybe 2kw+ and the cheapest premade thing I can find is $3500. Maybe I'll just use a carbon pile load but that will be much less accurate.
