Your machine can connect to an exchange so that bitcoin is automatically purchased at market rates with each bill that's inserted. In this way the price volatility of bitcoin is mitigated. Bitstamp trading is support for all currencies.
Flow with Bitstamp trading
When linked to an exchange, the flow is: user inserts bills, machine places buy order with each bill inserted, bitcoins are sent from the machine's hot wallet to the user. The module will purchase the same amount of bitcoins that is dispensed to the user.
For security purposes, the admin does not initiate a withdrawal of bitcoin from your trading account to your hot wallet. You should periodically top up your machine's wallet.
Please note: Though trading will occur with the machine on any currency at Bitstamp's USD market rates, their ticker API currently only supports USD or EUR. Please set your price source to any of the three other options than Bitstamp if using another currency.
To trade on Bitstamp, create a new API key from within your account. Go to Security, then API Access.
Click on 'New API key', then check the 'Account balance' and 'Buy limit order' permission boxes. For the security of your account balance, do not enable any others.
Click 'Generate key'. In the screen that follows, copy the Key and Secret fields, pasting them into the Trading section of your admin along with your Bitstamp ID.
On Bitstamp, click 'Activate' next to your secret key. Check your email for an activation link and follow it to enable.
Test some purchases using an amount greater than $5 USD (the minimum trade Bitstamp allows.)