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What is the Re:load Pro, and why do I need one?
The Re:Load Pro is an active load. It acts as a current sink, always drawing the same amount of current regardless of the voltage across it.
Active loads are incredibly useful for all sorts of electronics testing requirements. You can use one to see how a power supply performs under load, check if a battery lives up to its manufacturer's specifications for capacity or current draw, test motor drivers, or a variety of common constant-current tasks, such as testing LEDs, or even doing electroplating. With computer control of the load, you can even do your own IV-curve tracing.
The original Re:load was born out of my frustration at being unable to find a reasonably priced active load for my fairly modest testing needs. Commercial units typically cost several hundred or even thousand dollars and require substantial bench space - far from ideal for a hobbyist.
The Re:load has turned out to be an incredibly useful device for many people, but while its minimalist feature set is well suited to some applications, often you want something with a bit more oomph, better precision, or extra features. That's where the Re:load Pro comes in.
The Re:load Pro takes the robust design of the original Re:load and rebuilds it around a microcontroller. As a result, it offers a USB interface for power and control/monitoring, a good quality backlit display, and accurate voltage and current measurement. And that's just for starters!
The Re:load Pro's features include:
- Dissipate 25 watts continuously, or more for short periods. Even more with the forthcoming fan kit (see below!)
- Handle up to 6 amps or 60 volts. Works right down to 0V, too!
- Easy to use and intuitive user-interface.
- Current adjustable with milliamp precision over the whole range.
- Protection against overcurrent, overvoltage, overtemperature, ESD, and reverse polarity.
- Power supplied over USB from either a computer or a USB charger.
- Fully isolated USB interface. Your computer is isolated from any direct interaction with dangerous voltages and currents.
- Fully controllable over USB, with monitoring functionality. You can use your computer to program in a profile!
- Configurable display, showing voltage, current, power, resistance, and total energy dissipated.
- Open Source, with a USB bootloader, so you don't need expensive development tools if you want to make your own modifications. Firmware updates will be easy to install, too!
I've saved the best feature for last: You can have one of your own, soon! Since two production prototypes have already been produced, and the manufacturing chain lined up, there's no nine to twelve month wait here; we can start production as soon as the Kickstarter concludes, getting units into your hands as little as 2 months from today!
What's inside the box?
The Re:load Pro's heart is a PSoC 4 microcontroller, from Cypress. The PSoC 4 combines an ARM Cortex M0 processor with configurable digital and analog blocks, making it possible to design incredibly flexible digital and analog solutions. This is ideal for the Re:load Pro, because it both cuts down on external components, which reduces cost and improves reliability, and makes it more flexible since a greater degree of the circuit is under firmware control.
The PSoC 4 in the Re:load Pro includes an integrated opamp, which the Re:load Pro uses to implement the active load functionality. Sophisticated features like a trim register and configurable compensation make it possible to wring the absolute best performance out of the opamp.
The other vital component of the Re:load Pro is the pass transistor - a BTS141. This unique component from Infineon acts like a regular FET transistor, but incorporates built in overcurrent, overvoltage, ESD and overtemperature protection. The BTS141 is a large part of what makes the Re:load so robust.
The heatsink and the enclosure are both high quality black anodised Aluminium. The heatsink is a custom extrusion, designed specifically for the Re:load Pro.
The standard Re:load Pro kit comes with just the Re:load Pro - you need to supply the USB cable and test cables. We also have a "batteries included" option, which includes:
- One Re:load Pro
- One USB cable, with a right-angle connector on the device end.
- A pair of test leads with banana terminals on one end and alligator clips on the other.
- A deck of Circuit Patterns Trading Cards.
What's this about a fan kit?
While the Re:load Pro was designed to be absolutely silent with passive cooling, adding even a little active cooling with some small fans can substantially increase the maximum continuous load the Re:load Pro can handle. Although it comes passively cooled by default, I've designed the PCB and the heatsink with optional active cooling in mind.
Once the Re:load Pro design is finalised and ready to be manufactured, I plan to start work on a fan kit. The fan kit will consist of two small fans and a mounting plate that attaches to the heatsink - you can see the thick fins on either side that it's intended to attach to - as well as a PCB with a fan controller that plugs into an expansion slot on the Re:load Pro.
Fan kits will be available as a separate add-on, and threaded holes to mount it will be provided on the Re:load. You'll need a screwdriver, and a soldering iron to attach the fan controller expansion PCB.
Are there stretch goals!
- £10,000 - Accessory jack on front panel, allowing functionality such as analog voltage readout, triggering oscilloscopes, and accepting trigger signals. - Unlocked!
- £12,000 - "Batteries included" option upgraded to include banana to banana cables with alligator clip adapter. - Unlocked!
- £15,000 - Upgrade to shrouded connectors for the banana terminals. - Unlocked!
- £20,000: Everyone gets 20% off the fan kit - Unlocked!
- £25,000: Fancy black USB socket instead of the boring white one. Everyone gets 25% off the fan kit.
- £30,000: Everyone gets 30% off the fan kit
- £42,000: Hotblack Desiato edition of the Re:load Pro. Black knob, with black silkscreen, black on black display and black backlight.
- £50,000: Everyone gets 50% off the fan kit!
Is it Open Source?
Yes! Everything from Arachnid Labs is open source. The Re:load Pro is licensed under the Apache Public License, and you can get the current source code and schematics right here.
What's the current status of the Re:load Pro?
The second prototype - shown in the video and photos - is fully functional, and the firmware is approximately 80% complete. What you see in the video is very close to what you'll be getting, only with even more polish.
Aside from firmware improvements, there are a few minor changes to be made to the hardware for mass production. Before ordering the production units, I'll do another prototype run with these changes to make certain that everything is working as expected.
Since most of the primary engineering is already done, most of what remains is production. I've already nailed down all the important details; here's the expected production timeline:
- May 5: Kickstarter finishes. Orders placed with fab, as well as heatsink and enclosure manufacturers, for shipping direct to the fab.
- May 19 - June 6: Components arrive at US fabrication facility.
- May 26 - June 23: Production prototype units built and tested by fab.
- May 29 - June 30: Production prototype arrives in the UK for testing, evaluation, and approval.
- May 30 - June 31: Fab gets approval for full production run and starts working. Firmware 'goes gold'.
- June 12 - July 21: Fab finishes production of first batch of units, starts shipping. Second batch begins production.
- June 19 - July 28: Units start to arrive in your hands, ready to be put to use!
Each batch is 200 units. That means that if your order is in the first 200, best case, you'll have a Re:Load in your hands mid to late June; worst case July, barring the truly unexpected! The factory can do about 200 units a month after the first batch, and we're prepared to scale up production if things get really popular.
This is a reasonably tight production schedule, but I've worked each step out, and believe it's realistic.
Risks and challenges
With two prototypes already constructed and fully functional, and the custom heatsink extrusion already manufactured and tested, the riskiest part is done. From here on in, the biggest question is whether any unexpected delays will jeopardise the shipping deadline.
The manufacturers of the heatsink and enclosure could take longer than expected to provide their components; the assembly house could take longer than expected to produce finished units, or some parts could go unexpectedly out of stock.
While it's impossible to guard against these possibilities completely, I've done everything I can to ensure the risks are minimised, and I'm in close contact with all the suppliers to make sure I'm aware if anything changes.
As far as meeting the schedule goes, the areas of largest uncertainty are the approval of the prototype, and shipping. Since the changes between the current version and the production prototype are very minor, I don't anticipate any problems in that area. Shipping is more unpredictable, but by shipping from two locations - London and Texas - we minimise the time to get Re:loads into your hands, and reduce the unpredictability of international shipping as much as possible.Learn about accountability on Kickstarter
- (21 days)