Hi there,
I've designed a fist-sized programmable resistance box QR10, it can be controlled via USB-COM port or keypad.
I've thinking it for quite a long time that does it helps in audio field if I modified it as a potentiometer? Then you might control it automatically for high-end loudspeakers or as a smart gain control for op. amplifiers.
Advantages compared to the semiconductor resistor chips or mechanical potentiometers:
Some additional work still need to be done to modify QR10 as a potentiometer. But I think it's also possible to DIY one by adding an external fix value resistor.
Any comments or suggestions will be appreciated.
I've designed a fist-sized programmable resistance box QR10, it can be controlled via USB-COM port or keypad.
I've thinking it for quite a long time that does it helps in audio field if I modified it as a potentiometer? Then you might control it automatically for high-end loudspeakers or as a smart gain control for op. amplifiers.
Advantages compared to the semiconductor resistor chips or mechanical potentiometers:
- High accuracy, output resistance tolerance can within 0.01%. Accuracy of potentiometer ratio can be even higher.
- TCR as low as 15ppm/25ppm so no worry about temperature drift.
- High resolution. A model that range from 1 Ω to 630 kΩ is with 0.1Ω steps, which means 6,300,000 steps in total (you can calculate how small a dB steps it could reach)
- And low cost.
Some additional work still need to be done to modify QR10 as a potentiometer. But I think it's also possible to DIY one by adding an external fix value resistor.
Any comments or suggestions will be appreciated.
Can you give some more info? What is the resistive element? Resistors, switched? Switched by what?
What is the law, linear, log, programmable?
I like the idea with the buttons and display, but more for test equipment than on an amplifier.
(I did read the user guide on your website).
Jan
What is the law, linear, log, programmable?
I like the idea with the buttons and display, but more for test equipment than on an amplifier.
(I did read the user guide on your website).
Jan
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Yes, you're right. it's designed as a equipment rather than a module or component.
The basic law is based on "relay-resistor" topology, the relay is mechanical latching relay while the resistor is MELF. You can find more info. about its background here (hope it not being treated as Ad)
Channing
Does it have a separate power input? it would be preferable to have the OLED etc out of the electronics circuit.
Reading the manual:
So it has a LiPo in the body - is that charged by the USB? Can it work whilst charging?
Perhaps a marketing block diagram showing a m-architecture would answer a few questions. It doesn't need to give the secrets away, simply have blocks between with line connections between the external terminals to the switched resistance array, a block for digital control with an isolated line to the switch array, the isolated USB socket and power connecting to the LiPo recharge.
That way people know if you plug in it will charge the LiPo and answer if it also powers the digital when plugged in or they have to wait for the LiPo.
I didn't note if there's an audible alarm for when the LiPo is low enough battery that it risks a switching failure.
Also it's not clear if the block retains it's set resistance in the event of the LiPo battery being exhausted, or, if the resistance is undefined or completely disconnected.
Nice looking product so far - the OLED is a little small for reading from across the bench.
You may also want the maximum voltage rating on the top in print. If at a later date you have higher voltage offerings and someone has a couple on the bench it will stop accidents..
Reading the manual:
So it has a LiPo in the body - is that charged by the USB? Can it work whilst charging?
Perhaps a marketing block diagram showing a m-architecture would answer a few questions. It doesn't need to give the secrets away, simply have blocks between with line connections between the external terminals to the switched resistance array, a block for digital control with an isolated line to the switch array, the isolated USB socket and power connecting to the LiPo recharge.
That way people know if you plug in it will charge the LiPo and answer if it also powers the digital when plugged in or they have to wait for the LiPo.
I didn't note if there's an audible alarm for when the LiPo is low enough battery that it risks a switching failure.
Also it's not clear if the block retains it's set resistance in the event of the LiPo battery being exhausted, or, if the resistance is undefined or completely disconnected.
Nice looking product so far - the OLED is a little small for reading from across the bench.
You may also want the maximum voltage rating on the top in print. If at a later date you have higher voltage offerings and someone has a couple on the bench it will stop accidents..
Yes. MCU and driver circuit is completely isolated with the resistance output path.
Yes and yes.
Very very good point. I sometimes missed this angle of view since myself "know" every part of it and ,sure, I should put my feet into your shoes.
When it's under 3.6V or so, you cannot turn it on. And it will be forced to shutdown if under 3.6V. I should have mentioned this feature.
It's latching relay and it will keep the resistance value even shut down.
Thanks. Aha, old men sometimes complain about tiny OLED issue🙂
Yes, it does print the max volatage allowed on the 1st row. And people should always be careful when using such equipment (although user can define the min output limiter in advance).
Ideally it's constant (the matching curve should be a straight line). However, due to the tolerance of the base resistors, for example, for a 1.0 Ω step model in general it doesn't output exactly 100.0 Ω or 101.0 Ω, , it will output 99.5 Ω or 101.3 Ω instead.
Here is the check data of a random sample of 0.125Ω steps:
It would also be good to understand the tolerance - given a ±1%+1% isn't 1%, so that's also defined by the resistor array configuration.
On the voltage rating - having it printed on the outside saves having to power up to select the right one. My experience of products and services - make it as frictionless for the customer as possible. That way I'd not try and use it for a 640Vdc circuit rather than a 100V circuit. Just add it to the anodised screen print.
I may be old but the recent eye test this year showed 0.5% vision from perfect 😉 so don't need to wear glasses 😀 Think of it as a grumpy aged tech with tired eyes staring through glasses/under the magnifying classes to check.. grumpy customers don't have patience to try to read small screens 😛 they usually replace the unit with a larger screen and then add it to their YouTube channels.
On the voltage rating - having it printed on the outside saves having to power up to select the right one. My experience of products and services - make it as frictionless for the customer as possible. That way I'd not try and use it for a 640Vdc circuit rather than a 100V circuit. Just add it to the anodised screen print.
I may be old but the recent eye test this year showed 0.5% vision from perfect 😉 so don't need to wear glasses 😀 Think of it as a grumpy aged tech with tired eyes staring through glasses/under the magnifying classes to check.. grumpy customers don't have patience to try to read small screens 😛 they usually replace the unit with a larger screen and then add it to their YouTube channels.
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It's defined by PV (Process Value or in other words, “claimed output value”). PV in general is more or less close to SP (SetPoint). QR10 knows each resistor's actual vaule so it handles the combination of relay status (ON/OFF) to choose a closest one for the desired output.
Good point. I'll consider it and creat a voltage-resistance table for it.
Haha, 😳I actually don't know your age... I mean no harm... I can imagine one day I might be that type of old grumpy tech...