diff --git a/scripts/speed_reader.py b/scripts/speed_reader.py
index f1406e2..a3eaa7e 100644
--- a/scripts/speed_reader.py
+++ b/scripts/speed_reader.py
@@ -2,7 +2,7 @@ from src.variables.service import get_variable, set_variable
 from gpiozero import Button
 import datetime
 
-
+pulses_per_rotation = 1
 reader = Button(4)
 set_variable("speed_reader_last_impulse_time", datetime.datetime.now(), False)
 
@@ -11,11 +11,11 @@ def event():
     actual = datetime.datetime.now()
     last = get_variable("speed_reader_last_impulse_time")
     difference = (actual - last).total_seconds()
+    set_variable("speed_reader_last_impulse_time", actual, False)
 
-    if difference != 0:
-        return
+    rpm = (60 / difference) / pulses_per_rotation    
     
-    set_variable("pokus", difference)
+    set_variable("actual_rpm", rpm, False)
 
 
 
diff --git a/src/variables/router.py b/src/variables/router.py
index 48cb5ec..1a07bc0 100644
--- a/src/variables/router.py
+++ b/src/variables/router.py
@@ -13,7 +13,7 @@ def set_variable(variable: str, params: SetVariable):
 @router.get("/{variable}", description="Get variable data", response_model=str)
 def get_variable(variable: str):
     try:
-        return service.get_variable(variable=variable)
+        return str(service.get_variable(variable=variable))
     except:
         raise HTTPException(status_code=status.HTTP_404_NOT_FOUND)