T
Tim Angus
Guest
I better start by apologising in advance. My electronics expertise doesn't
extend much beyond what I learnt at high school, and that was 6 years ago.
As such I may be found to be talking out my ass to a certain extent.
I doubt the background to my problem is particularly important, but I
shall state it regardless. I am currently attempting to build input
devices for a Roland electronic drum module. One of these input devices
controls the hi hat. The commercial hi hat pedal senses foot pressure
using a force sensing resistor. I've searched high and low for a place to
get such devices in the UK in low volume, but I've not come up with
anything.
I did come up with an alternative however, in the form of part of the PCB
from an XBOX games console controller. It has a set of buttons which
control analog devices behaving relatively similarly to what the afore
mentioned Roland drum module expects on its pedal input. But not similarly
enough.
This input measures the resistance across its 5V line and ground. The
device which you connect to the input must have a resistance range from at
least 50KOhms to 0Ohms (or very close). The device I've hacked up from the
games controller has a range of infinity Ohms (i.e. open) to about 5KOhms.
As a result I need to transform its resistance to map to a range which the
drum module understands.
I've come up with the following naive circuit:
5V ----------------------
| |
F |
S |
R |
| /
|-------|
| \.
T |
V |
R |
| |
0V ----------------------
Where FSR is the hacked up force sensing resistor, TVR is a trimming
variable resistor, and the jumble on the right is an NPN transistor. So,
this sort of works as far as the range of the resistance is correct. When
pressing the FSR though, as soon as the base voltage passes 0.6V the
transistor closes rapidly. In other words the sensitivity of the device is
lost so much so that it is barely better than the momentary switch that it
replaces in my current setup.
So basically, am I doing anything right? Is there some adjustment to this
circuit, or entirely different circuit that would satisfy my requirement
to transpose the resistive range yet retain the sensitivity of the device?
Thanks, Tim.
extend much beyond what I learnt at high school, and that was 6 years ago.
As such I may be found to be talking out my ass to a certain extent.
I doubt the background to my problem is particularly important, but I
shall state it regardless. I am currently attempting to build input
devices for a Roland electronic drum module. One of these input devices
controls the hi hat. The commercial hi hat pedal senses foot pressure
using a force sensing resistor. I've searched high and low for a place to
get such devices in the UK in low volume, but I've not come up with
anything.
I did come up with an alternative however, in the form of part of the PCB
from an XBOX games console controller. It has a set of buttons which
control analog devices behaving relatively similarly to what the afore
mentioned Roland drum module expects on its pedal input. But not similarly
enough.
This input measures the resistance across its 5V line and ground. The
device which you connect to the input must have a resistance range from at
least 50KOhms to 0Ohms (or very close). The device I've hacked up from the
games controller has a range of infinity Ohms (i.e. open) to about 5KOhms.
As a result I need to transform its resistance to map to a range which the
drum module understands.
I've come up with the following naive circuit:
5V ----------------------
| |
F |
S |
R |
| /
|-------|
| \.
T |
V |
R |
| |
0V ----------------------
Where FSR is the hacked up force sensing resistor, TVR is a trimming
variable resistor, and the jumble on the right is an NPN transistor. So,
this sort of works as far as the range of the resistance is correct. When
pressing the FSR though, as soon as the base voltage passes 0.6V the
transistor closes rapidly. In other words the sensitivity of the device is
lost so much so that it is barely better than the momentary switch that it
replaces in my current setup.
So basically, am I doing anything right? Is there some adjustment to this
circuit, or entirely different circuit that would satisfy my requirement
to transpose the resistive range yet retain the sensitivity of the device?
Thanks, Tim.